feat(api): Add vector store file batches api (#3642)

# What does this PR do?

Add Open AI Compatible vector store file batches api. This functionality
is needed to attach many files to a vector store as a batch.
https://github.com/llamastack/llama-stack/issues/3533

API Stubs have been merged
https://github.com/llamastack/llama-stack/pull/3615
Adds persistence for file batches as discussed in diff
https://github.com/llamastack/llama-stack/pull/3544
(Used claude code for generation and reviewed by me)


## Test Plan
1. Unit tests pass
2. Also verified the cc-vec integration with LLamaStackClient works with
the file batches api. https://github.com/raghotham/cc-vec
2. Integration tests pass

llama_stack/providers/inline/vector_io/faiss/faiss.py

@@ -200,12 +200,10 @@ class FaissIndex(EmbeddingIndex):
 
 class FaissVectorIOAdapter(OpenAIVectorStoreMixin, VectorIO, VectorDBsProtocolPrivate):
     def __init__(self, config: FaissVectorIOConfig, inference_api: Inference, files_api: Files | None) -> None:
+        super().__init__(files_api=files_api, kvstore=None)
         self.config = config
         self.inference_api = inference_api
-        self.files_api = files_api
         self.cache: dict[str, VectorDBWithIndex] = {}
-        self.kvstore: KVStore | None = None
-        self.openai_vector_stores: dict[str, dict[str, Any]] = {}
 
     async def initialize(self) -> None:
         self.kvstore = await kvstore_impl(self.config.kvstore)

llama_stack/providers/inline/vector_io/sqlite_vec/sqlite_vec.py

@@ -410,12 +410,10 @@ class SQLiteVecVectorIOAdapter(OpenAIVectorStoreMixin, VectorIO, VectorDBsProtoc
     """
 
     def __init__(self, config, inference_api: Inference, files_api: Files | None) -> None:
+        super().__init__(files_api=files_api, kvstore=None)
         self.config = config
         self.inference_api = inference_api
-        self.files_api = files_api
         self.cache: dict[str, VectorDBWithIndex] = {}
-        self.openai_vector_stores: dict[str, dict[str, Any]] = {}
-        self.kvstore: KVStore | None = None
 
     async def initialize(self) -> None:
         self.kvstore = await kvstore_impl(self.config.kvstore)