chore: OpenAI compatibility for Milvus (#2470)

# What does this PR do?
Closes https://github.com/meta-llama/llama-stack/issues/2461



## Test Plan
Tested with the `ollama` distriubtion template and updated the vector_io
provider to:
```yaml
vector_io:
- provider_id: milvus
  provider_type: inline::milvus
  config:
    db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/ollama}/milvus_store.db
    kvstore:
      type: sqlite
      db_name: milvus_registry.db
```

Ran the stack
```bash
llama stack run ./llama_stack/templates/ollama/run.yaml --image-type venv --env OLLAMA_URL="http://0.0.0.0:11434"
```

Ran the tests:
```
pytest -sv --stack-config=http://localhost:8321 tests/integration/vector_io/test_openai_vector_stores.py  --embedding-model all-MiniLM-L6-v2
```
Output passed.

Signed-off-by: Francisco Javier Arceo <farceo@redhat.com>

llama_stack/templates/starter/build.yaml

@@ -15,6 +15,7 @@ distribution_spec:
     - inline::sentence-transformers
     vector_io:
     - inline::sqlite-vec
+    - inline::milvus
     - remote::chromadb
     - remote::pgvector
     files:

llama_stack/templates/starter/run.yaml

@@ -72,6 +72,14 @@ providers:
     provider_type: inline::sqlite-vec
     config:
       db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/starter}/sqlite_vec.db
+  - provider_id: ${env.ENABLE_MILVUS:+milvus}
+    provider_type: inline::milvus
+    config:
+      db_path: ${env.MILVUS_DB_PATH:=~/.llama/distributions/starter/milvus.db}
+      kvstore:
+        type: sqlite
+        namespace: null
+        db_path: ${env.SQLITE_STORE_DIR:=~/.llama/distributions/starter}/${env.MILVUS_KVSTORE_DB_PATH:=~/.llama/distributions/starter/milvus_registry.db}
   - provider_id: ${env.ENABLE_CHROMADB:+chromadb}
     provider_type: remote::chromadb
     config:

llama_stack/templates/starter/starter.py

@@ -17,6 +17,9 @@ from llama_stack.providers.inline.inference.sentence_transformers import (
     SentenceTransformersInferenceConfig,
 )
 from llama_stack.providers.inline.vector_io.faiss.config import FaissVectorIOConfig
+from llama_stack.providers.inline.vector_io.milvus.config import (
+    MilvusVectorIOConfig,
+)
 from llama_stack.providers.inline.vector_io.sqlite_vec.config import (
     SQLiteVectorIOConfig,
 )
@@ -151,7 +154,7 @@ def get_distribution_template() -> DistributionTemplate:
     inference_providers, available_models = get_inference_providers()
     providers = {
         "inference": ([p.provider_type for p in inference_providers] + ["inline::sentence-transformers"]),
-        "vector_io": ["inline::sqlite-vec", "remote::chromadb", "remote::pgvector"],
+        "vector_io": ["inline::sqlite-vec", "inline::milvus", "remote::chromadb", "remote::pgvector"],
         "files": ["inline::localfs"],
         "safety": ["inline::llama-guard"],
         "agents": ["inline::meta-reference"],
@@ -179,6 +182,11 @@ def get_distribution_template() -> DistributionTemplate:
             provider_type="inline::sqlite-vec",
             config=SQLiteVectorIOConfig.sample_run_config(f"~/.llama/distributions/{name}"),
         ),
+        Provider(
+            provider_id="${env.ENABLE_MILVUS:+milvus}",
+            provider_type="inline::milvus",
+            config=MilvusVectorIOConfig.sample_run_config(f"~/.llama/distributions/{name}"),
+        ),
         Provider(
             provider_id="${env.ENABLE_CHROMADB:+chromadb}",
             provider_type="remote::chromadb",