feat: implement get chat completions APIs (#2200)

# What does this PR do?
* Provide sqlite implementation of the APIs introduced in
https://github.com/meta-llama/llama-stack/pull/2145.
* Introduced a SqlStore API: llama_stack/providers/utils/sqlstore/api.py
and the first Sqlite implementation
* Pagination support will be added in a future PR.

## Test Plan
Unit test on sql store:
<img width="1005" alt="image"
src="https://github.com/user-attachments/assets/9b8b7ec8-632b-4667-8127-5583426b2e29"
/>


Integration test:
```
INFERENCE_MODEL="llama3.2:3b-instruct-fp16" llama stack build --template ollama --image-type conda --run
```
```
LLAMA_STACK_CONFIG=http://localhost:5001 INFERENCE_MODEL="llama3.2:3b-instruct-fp16" python -m pytest -v tests/integration/inference/test_openai_completion.py --text-model "llama3.2:3b-instruct-fp16" -k 'inference_store and openai'
```

llama_stack/providers/utils/sqlstore/sqlstore.py

@@ -0,0 +1,72 @@
+# Copyright (c) Meta Platforms, Inc. and affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the terms described in the LICENSE file in
+# the root directory of this source tree.
+
+
+from enum import Enum
+from pathlib import Path
+from typing import Annotated, Literal
+
+from pydantic import BaseModel, Field
+
+from llama_stack.distribution.utils.config_dirs import RUNTIME_BASE_DIR
+
+from .api import SqlStore
+
+
+class SqlStoreType(Enum):
+    sqlite = "sqlite"
+    postgres = "postgres"
+
+
+class SqliteSqlStoreConfig(BaseModel):
+    type: Literal["sqlite"] = SqlStoreType.sqlite.value
+    db_path: str = Field(
+        default=(RUNTIME_BASE_DIR / "sqlstore.db").as_posix(),
+        description="Database path, e.g. ~/.llama/distributions/ollama/sqlstore.db",
+    )
+
+    @property
+    def engine_str(self) -> str:
+        return "sqlite+aiosqlite:///" + Path(self.db_path).expanduser().as_posix()
+
+    @classmethod
+    def sample_run_config(cls, __distro_dir__: str, db_name: str = "sqlstore.db"):
+        return cls(
+            type="sqlite",
+            db_path="${env.SQLITE_STORE_DIR:" + __distro_dir__ + "}/" + db_name,
+        )
+
+    # TODO: move this when we have a better way to specify dependencies with internal APIs
+    @property
+    def pip_packages(self) -> list[str]:
+        return ["sqlalchemy[asyncio]"]
+
+
+class PostgresSqlStoreConfig(BaseModel):
+    type: Literal["postgres"] = SqlStoreType.postgres.value
+
+    @property
+    def pip_packages(self) -> list[str]:
+        raise NotImplementedError("Postgres is not implemented yet")
+
+
+SqlStoreConfig = Annotated[
+    SqliteSqlStoreConfig | PostgresSqlStoreConfig,
+    Field(discriminator="type", default=SqlStoreType.sqlite.value),
+]
+
+
+def sqlstore_impl(config: SqlStoreConfig) -> SqlStore:
+    if config.type == SqlStoreType.sqlite.value:
+        from .sqlite.sqlite import SqliteSqlStoreImpl
+
+        impl = SqliteSqlStoreImpl(config)
+    elif config.type == SqlStoreType.postgres.value:
+        raise NotImplementedError("Postgres is not implemented yet")
+    else:
+        raise ValueError(f"Unknown sqlstore type {config.type}")
+
+    return impl