Refa: migrate chat models to LiteLLM (#9394)

### What problem does this PR solve?

All models pass the mock response tests, which means that if a model can
return the correct response, everything should work as expected.
However, not all models have been fully tested in a real environment,
the real API_KEY. I suggest actively monitoring the refactored models
over the coming period to ensure they work correctly and fixing them
step by step, or waiting to merge until most have been tested in
practical environment.

### Type of change

- [x] Refactoring

api/db/services/llm_service.py

@@ -141,6 +141,7 @@ class TenantLLMService(CommonService):
     @DB.connection_context()
     def model_instance(cls, tenant_id, llm_type, llm_name=None, lang="Chinese", **kwargs):
         model_config = TenantLLMService.get_model_config(tenant_id, llm_type, llm_name)
+        kwargs.update({"provider": model_config["llm_factory"]})
         if llm_type == LLMType.EMBEDDING.value:
             if model_config["llm_factory"] not in EmbeddingModel:
                 return