feat(responses): implement usage tracking in streaming responses (#3771)

Implementats usage accumulation to StreamingResponseOrchestrator. 

The most important part was to pass `stream_options = { "include_usage":
true }` to the chat_completion call. This means I will have to record
all responses tests again because request hash will change :)

Test changes:
- Add usage assertions to streaming and non-streaming tests
- Update test recordings with actual usage data from OpenAI

tests/unit/providers/agents/meta_reference/test_openai_responses.py

@@ -167,6 +167,9 @@ async def test_create_openai_response_with_string_input(openai_responses_impl, m
         tools=None,
         stream=True,
         temperature=0.1,
+        stream_options={
+            "include_usage": True,
+        },
     )
 
     # Should have content part events for text streaming