feat: update search for vector_stores (#2441)

Updated the `search` functionality return response to match openai. 

## Test Plan
```
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

@@ -2734,7 +2734,7 @@ paths:
           content:
             application/json:
               schema:
-                $ref: '#/components/schemas/VectorStoreSearchResponse'
+                $ref: '#/components/schemas/VectorStoreSearchResponsePage'
         '400':
           $ref: '#/components/responses/BadRequest400'
         '429':
@@ -9190,7 +9190,48 @@ components:
       required:
         - query
       title: OpenaiSearchVectorStoreRequest
+    VectorStoreContent:
+      type: object
+      properties:
+        type:
+          type: string
+          const: text
+        text:
+          type: string
+      additionalProperties: false
+      required:
+        - type
+        - text
+      title: VectorStoreContent
     VectorStoreSearchResponse:
+      type: object
+      properties:
+        file_id:
+          type: string
+        filename:
+          type: string
+        score:
+          type: number
+        attributes:
+          type: object
+          additionalProperties:
+            oneOf:
+              - type: string
+              - type: number
+              - type: boolean
+        content:
+          type: array
+          items:
+            $ref: '#/components/schemas/VectorStoreContent'
+      additionalProperties: false
+      required:
+        - file_id
+        - filename
+        - score
+        - content
+      title: VectorStoreSearchResponse
+      description: Response from searching a vector store.
+    VectorStoreSearchResponsePage:
       type: object
       properties:
         object:
@@ -9201,15 +9242,7 @@ components:
         data:
           type: array
           items:
-            type: object
-            additionalProperties:
-              oneOf:
-                - type: 'null'
-                - type: boolean
-                - type: number
-                - type: string
-                - type: array
-                - type: object
+            $ref: '#/components/schemas/VectorStoreSearchResponse'
         has_more:
           type: boolean
           default: false
@@ -9221,7 +9254,7 @@ components:
         - search_query
         - data
         - has_more
-      title: VectorStoreSearchResponse
+      title: VectorStoreSearchResponsePage
       description: Response from searching a vector store.
     OpenaiUpdateVectorStoreRequest:
       type: object