feat: Add OpenAI compat /v1/vector_store APIs (#2423)

Adding OpenAI compat `/v1/vector-store` apis. 
This PR implements the `faiss` provider with followup PRs coming up for
other providers.

Added routes to create, update, delete, list vector stores. 
Also added route to search a vector store

Inserting into vector stores is missing and will be a follow up diff. 

### Test Plan 
- Added new integration test for testing the faiss provider 
```
pytest -sv --stack-config http://localhost:8321 tests/integration/vector_io/test_openai_vector_stores.py --embedding-model all-MiniLM-L6-v2
```

docs/_static/llama-stack-spec.yaml

@@ -2294,6 +2294,91 @@ paths:
             schema:
               $ref: '#/components/schemas/OpenaiCompletionRequest'
         required: true
+  /v1/openai/v1/vector_stores:
+    get:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreListResponse containing the list of vector stores.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreListResponse'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: Returns a list of vector stores.
+      parameters:
+        - name: limit
+          in: query
+          description: >-
+            A limit on the number of objects to be returned. Limit can range between
+            1 and 100, and the default is 20.
+          required: true
+          schema:
+            type: integer
+        - name: order
+          in: query
+          description: >-
+            Sort order by the `created_at` timestamp of the objects. `asc` for ascending
+            order and `desc` for descending order.
+          required: true
+          schema:
+            type: string
+        - name: after
+          in: query
+          description: >-
+            A cursor for use in pagination. `after` is an object ID that defines your
+            place in the list.
+          required: false
+          schema:
+            type: string
+        - name: before
+          in: query
+          description: >-
+            A cursor for use in pagination. `before` is an object ID that defines
+            your place in the list.
+          required: false
+          schema:
+            type: string
+    post:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreObject representing the created vector store.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreObject'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: Creates a vector store.
+      parameters: []
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/OpenaiCreateVectorStoreRequest'
+        required: true
   /v1/openai/v1/files/{file_id}:
     get:
       responses:
@@ -2356,6 +2441,100 @@ paths:
           required: true
           schema:
             type: string
+  /v1/openai/v1/vector_stores/{vector_store_id}:
+    get:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreObject representing the vector store.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreObject'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: Retrieves a vector store.
+      parameters:
+        - name: vector_store_id
+          in: path
+          description: The ID of the vector store to retrieve.
+          required: true
+          schema:
+            type: string
+    post:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreObject representing the updated vector store.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreObject'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: Updates a vector store.
+      parameters:
+        - name: vector_store_id
+          in: path
+          description: The ID of the vector store to update.
+          required: true
+          schema:
+            type: string
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/OpenaiUpdateVectorStoreRequest'
+        required: true
+    delete:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreDeleteResponse indicating the deletion status.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreDeleteResponse'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: Delete a vector store.
+      parameters:
+        - name: vector_store_id
+          in: path
+          description: The ID of the vector store to delete.
+          required: true
+          schema:
+            type: string
   /v1/openai/v1/embeddings:
     post:
       responses:
@@ -2546,6 +2725,46 @@ paths:
           required: true
           schema:
             type: string
+  /v1/openai/v1/vector_stores/{vector_store_id}/search:
+    post:
+      responses:
+        '200':
+          description: >-
+            A VectorStoreSearchResponse containing the search results.
+          content:
+            application/json:
+              schema:
+                $ref: '#/components/schemas/VectorStoreSearchResponse'
+        '400':
+          $ref: '#/components/responses/BadRequest400'
+        '429':
+          $ref: >-
+            #/components/responses/TooManyRequests429
+        '500':
+          $ref: >-
+            #/components/responses/InternalServerError500
+        default:
+          $ref: '#/components/responses/DefaultError'
+      tags:
+        - VectorIO
+      description: >-
+        Search for chunks in a vector store.
+
+        Searches a vector store for relevant chunks based on a query and optional
+        file attribute filters.
+      parameters:
+        - name: vector_store_id
+          in: path
+          description: The ID of the vector store to search.
+          required: true
+          schema:
+            type: string
+      requestBody:
+        content:
+          application/json:
+            schema:
+              $ref: '#/components/schemas/OpenaiSearchVectorStoreRequest'
+        required: true
   /v1/post-training/preference-optimize:
     post:
       responses:
@@ -8505,6 +8724,131 @@ components:
       title: OpenAICompletionChoice
       description: >-
         A choice from an OpenAI-compatible completion response.
+    OpenaiCreateVectorStoreRequest:
+      type: object
+      properties:
+        name:
+          type: string
+          description: A name for the vector store.
+        file_ids:
+          type: array
+          items:
+            type: string
+          description: >-
+            A list of File IDs that the vector store should use. Useful for tools
+            like `file_search` that can access files.
+        expires_after:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            The expiration policy for a vector store.
+        chunking_strategy:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            The chunking strategy used to chunk the file(s). If not set, will use
+            the `auto` strategy.
+        metadata:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            Set of 16 key-value pairs that can be attached to an object.
+        embedding_model:
+          type: string
+          description: >-
+            The embedding model to use for this vector store.
+        embedding_dimension:
+          type: integer
+          description: >-
+            The dimension of the embedding vectors (default: 384).
+        provider_id:
+          type: string
+          description: >-
+            The ID of the provider to use for this vector store.
+        provider_vector_db_id:
+          type: string
+          description: >-
+            The provider-specific vector database ID.
+      additionalProperties: false
+      title: OpenaiCreateVectorStoreRequest
+    VectorStoreObject:
+      type: object
+      properties:
+        id:
+          type: string
+        object:
+          type: string
+          default: vector_store
+        created_at:
+          type: integer
+        name:
+          type: string
+        usage_bytes:
+          type: integer
+          default: 0
+        file_counts:
+          type: object
+          additionalProperties:
+            type: integer
+        status:
+          type: string
+          default: completed
+        expires_after:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+        expires_at:
+          type: integer
+        last_active_at:
+          type: integer
+        metadata:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+      additionalProperties: false
+      required:
+        - id
+        - object
+        - created_at
+        - usage_bytes
+        - file_counts
+        - status
+        - metadata
+      title: VectorStoreObject
+      description: OpenAI Vector Store object.
     OpenAIFileDeleteResponse:
       type: object
       properties:
@@ -8528,6 +8872,24 @@ components:
       title: OpenAIFileDeleteResponse
       description: >-
         Response for deleting a file in OpenAI Files API.
+    VectorStoreDeleteResponse:
+      type: object
+      properties:
+        id:
+          type: string
+        object:
+          type: string
+          default: vector_store.deleted
+        deleted:
+          type: boolean
+          default: true
+      additionalProperties: false
+      required:
+        - id
+        - object
+        - deleted
+      title: VectorStoreDeleteResponse
+      description: Response from deleting a vector store.
     OpenaiEmbeddingsRequest:
       type: object
       properties:
@@ -8751,9 +9113,148 @@ components:
       required:
         - data
       title: OpenAIListModelsResponse
+    VectorStoreListResponse:
+      type: object
+      properties:
+        object:
+          type: string
+          default: list
+        data:
+          type: array
+          items:
+            $ref: '#/components/schemas/VectorStoreObject'
+        first_id:
+          type: string
+        last_id:
+          type: string
+        has_more:
+          type: boolean
+          default: false
+      additionalProperties: false
+      required:
+        - object
+        - data
+        - has_more
+      title: VectorStoreListResponse
+      description: Response from listing vector stores.
     Response:
       type: object
       title: Response
+    OpenaiSearchVectorStoreRequest:
+      type: object
+      properties:
+        query:
+          oneOf:
+            - type: string
+            - type: array
+              items:
+                type: string
+          description: >-
+            The query string or array for performing the search.
+        filters:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            Filters based on file attributes to narrow the search results.
+        max_num_results:
+          type: integer
+          description: >-
+            Maximum number of results to return (1 to 50 inclusive, default 10).
+        ranking_options:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            Ranking options for fine-tuning the search results.
+        rewrite_query:
+          type: boolean
+          description: >-
+            Whether to rewrite the natural language query for vector search (default
+            false)
+      additionalProperties: false
+      required:
+        - query
+        - max_num_results
+        - rewrite_query
+      title: OpenaiSearchVectorStoreRequest
+    VectorStoreSearchResponse:
+      type: object
+      properties:
+        object:
+          type: string
+          default: vector_store.search_results.page
+        search_query:
+          type: string
+        data:
+          type: array
+          items:
+            type: object
+            additionalProperties:
+              oneOf:
+                - type: 'null'
+                - type: boolean
+                - type: number
+                - type: string
+                - type: array
+                - type: object
+        has_more:
+          type: boolean
+          default: false
+        next_page:
+          type: string
+      additionalProperties: false
+      required:
+        - object
+        - search_query
+        - data
+        - has_more
+      title: VectorStoreSearchResponse
+      description: Response from searching a vector store.
+    OpenaiUpdateVectorStoreRequest:
+      type: object
+      properties:
+        name:
+          type: string
+          description: The name of the vector store.
+        expires_after:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            The expiration policy for a vector store.
+        metadata:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: 'null'
+              - type: boolean
+              - type: number
+              - type: string
+              - type: array
+              - type: object
+          description: >-
+            Set of 16 key-value pairs that can be attached to an object.
+      additionalProperties: false
+      title: OpenaiUpdateVectorStoreRequest
     DPOAlignmentConfig:
       type: object
       properties: