Fixes#4442 - async streaming fails with tool/function calls when
available_functions is not provided.
Added missing 'if tool_calls and not available_functions' handling to
4 OpenAI streaming methods:
- _handle_streaming_completion (sync Chat Completions)
- _ahandle_streaming_completion (async Chat Completions)
- _handle_streaming_responses (sync Responses API)
- _ahandle_streaming_responses (async Responses API)
The non-streaming counterparts already handle this case correctly.
The fix follows the same pattern used by the Azure provider.
Co-Authored-By: João <joao@crewai.com>
bd82aa9753