chore: turn OpenAIMixin into a pydantic.BaseModel

- implement get_api_key instead of relying on LiteLLMOpenAIMixin.get_api_key
 - remove use of LiteLLMOpenAIMixin
 - add default initialize/shutdown methods to OpenAIMixin
 - remove __init__s to allow proper pydantic construction
 - remove dead code from vllm adapter and associated / duplicate unit tests
 - update vllm adapter to use openaimixin for model registration
 - remove ModelRegistryHelper from fireworks & together adapters
 - remove Inference from nvidia adapter
 - complete type hints on embedding_model_metadata
 - allow extra fields on OpenAIMixin, for model_store, __provider_id__, etc
 - new recordings for ollama

tests/unit/providers/utils/inference/test_openai_mixin.py

@@ -13,6 +13,7 @@ from pydantic import BaseModel, Field
 from llama_stack.apis.inference import Model, OpenAIUserMessageParam
 from llama_stack.apis.models import ModelType
 from llama_stack.core.request_headers import request_provider_data_context
+from llama_stack.providers.utils.inference.model_registry import RemoteInferenceProviderConfig
 from llama_stack.providers.utils.inference.openai_mixin import OpenAIMixin
 
 
@@ -29,7 +30,7 @@ class OpenAIMixinImpl(OpenAIMixin):
 class OpenAIMixinWithEmbeddingsImpl(OpenAIMixinImpl):
     """Test implementation with embedding model metadata"""
 
-    embedding_model_metadata = {
+    embedding_model_metadata: dict[str, dict[str, int]] = {
         "text-embedding-3-small": {"embedding_dimension": 1536, "context_length": 8192},
         "text-embedding-ada-002": {"embedding_dimension": 1536, "context_length": 8192},
     }
@@ -38,7 +39,8 @@ class OpenAIMixinWithEmbeddingsImpl(OpenAIMixinImpl):
 @pytest.fixture
 def mixin():
     """Create a test instance of OpenAIMixin with mocked model_store"""
-    mixin_instance = OpenAIMixinImpl()
+    config = RemoteInferenceProviderConfig()
+    mixin_instance = OpenAIMixinImpl(config=config)
 
     # just enough to satisfy _get_provider_model_id calls
     mock_model_store = MagicMock()
@@ -53,7 +55,8 @@ def mixin():
 @pytest.fixture
 def mixin_with_embeddings():
     """Create a test instance of OpenAIMixin with embedding model metadata"""
-    return OpenAIMixinWithEmbeddingsImpl()
+    config = RemoteInferenceProviderConfig()
+    return OpenAIMixinWithEmbeddingsImpl(config=config)
 
 
 @pytest.fixture
@@ -504,7 +507,8 @@ class TestOpenAIMixinProviderDataApiKey:
     @pytest.fixture
     def mixin_with_provider_data_field(self):
         """Mixin instance with provider_data_api_key_field set"""
-        mixin_instance = OpenAIMixinWithProviderData()
+        config = RemoteInferenceProviderConfig()
+        mixin_instance = OpenAIMixinWithProviderData(config=config)
 
         # Mock provider_spec for provider data validation
         mock_provider_spec = MagicMock()