Refactor: Move return_hidden_states to the generate input (#3985)

Co-authored-by: Beichen-Ma <mabeichen12@gmail.com>

python/sglang/srt/entrypoints/engine.py

@@ -123,6 +123,7 @@ class Engine:
         top_logprobs_num: Optional[Union[List[int], int]] = None,
         lora_path: Optional[List[Optional[str]]] = None,
         custom_logit_processor: Optional[Union[List[str], str]] = None,
+        return_hidden_states: bool = False,
         stream: bool = False,
     ) -> Union[Dict, Iterator[Dict]]:
         """
@@ -144,6 +145,7 @@ class Engine:
             lora_path=lora_path,
             modalities=modalities_list,
             custom_logit_processor=custom_logit_processor,
+            return_hidden_states=return_hidden_states,
             stream=stream,
         )
         loop = asyncio.get_event_loop()