[router][grpc] Support streaming for v1/chat/completions (#11179)

sgl-router/benches/request_processing.rs

@@ -192,7 +192,6 @@ fn create_large_chat_completion_request() -> ChatCompletionRequest {
             content: Some(format!("Answer {}: This is a detailed response about topic {} that covers multiple aspects and provides comprehensive analysis of the interconnected systems you mentioned.", i, i)),
             name: None,
             tool_calls: None,
-            function_call: None,
             reasoning_content: None,
         });
     }