rebase: adapt to vLLM v0.29 APIs

Signed-off-by: tzhouam <tzhouam@connect.ust.hk>

tests/entrypoints/openai_api/test_serving_chat_metrics.py

@@ -19,7 +19,7 @@ pytestmark = [pytest.mark.core_model, pytest.mark.cpu]
 
 def test_omni_chat_completion_response_metrics():
     """Test OmniChatCompletionResponse metrics field works correctly."""
-    from vllm.entrypoints.openai.engine.protocol import UsageInfo
+    from vllm.entrypoints.serve.engine.protocol import UsageInfo
 
     from vllm_omni.entrypoints.openai.protocol.chat_completion import (
         OmniChatCompletionResponse,