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/templates/meta-reference-gpu/build.yaml

@@ -29,3 +29,6 @@ distribution_spec:
     - inline::rag-runtime
     - remote::model-context-protocol
 image_type: conda
+additional_pip_packages:
+- sqlalchemy[asyncio]
+- sqlalchemy[asyncio]

llama_stack/templates/meta-reference-gpu/run-with-safety.yaml

@@ -117,6 +117,9 @@ providers:
 metadata_store:
   type: sqlite
   db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/meta-reference-gpu}/registry.db
+inference_store:
+  type: sqlite
+  db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/meta-reference-gpu}/inference_store.db
 models:
 - metadata: {}
   model_id: ${env.INFERENCE_MODEL}

llama_stack/templates/meta-reference-gpu/run.yaml

@@ -107,6 +107,9 @@ providers:
 metadata_store:
   type: sqlite
   db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/meta-reference-gpu}/registry.db
+inference_store:
+  type: sqlite
+  db_path: ${env.SQLITE_STORE_DIR:~/.llama/distributions/meta-reference-gpu}/inference_store.db
 models:
 - metadata: {}
   model_id: ${env.INFERENCE_MODEL}