[ perf ] Replace json-> orjson in hot path (#11221)

Signed-off-by: vincentzed <207368749+vincentzed@users.noreply.github.com>

python/sglang/srt/function_call/utils.py

@@ -3,6 +3,7 @@ from json import JSONDecodeError, JSONDecoder
 from json.decoder import WHITESPACE
 from typing import Any, List, Literal, Optional, Tuple, Union
 
+import orjson
 import partial_json_parser
 from partial_json_parser.core.options import Allow
 
@@ -51,7 +52,7 @@ def _partial_json_loads(input_str: str, flags: Allow) -> Tuple[Any, int]:
 
 def _is_complete_json(input_str: str) -> bool:
     try:
-        json.loads(input_str)
+        orjson.loads(input_str)
         return True
     except JSONDecodeError:
         return False