feat: enhance InternalInstructor to support multiple LLM providers (#3767)

* feat: enhance InternalInstructor to support multiple LLM providers

- Updated InternalInstructor to conditionally create an instructor client based on the LLM provider.
- Introduced a new method _create_instructor_client to handle client creation using the modern from_provider pattern.
- Added functionality to extract the provider from the LLM model name.
- Implemented tests for InternalInstructor with various LLM providers including OpenAI, Anthropic, Gemini, and Azure, ensuring robust integration and error handling.

This update improves flexibility and extensibility for different LLM integrations.

* fix test

lib/crewai/tests/agents/test_agent.py

@@ -902,7 +902,8 @@ def test_agent_step_callback():
 
 @pytest.mark.vcr(filter_headers=["authorization"])
 def test_agent_function_calling_llm():
-    llm = "gpt-4o"
+    from crewai.llm import LLM
+    llm = LLM(model="gpt-4o", is_litellm=True)
 
     @tool
     def learn_about_ai() -> str: