[Bugfix] Migrate to REGEX Library to prevent catastrophic backtracking (#18454)

Signed-off-by: Crucifixion-Fxl <xmufxl@gmail.com>
Co-authored-by: Crucifixion-Fxl <xmufxl@gmail.com>

tests/v1/entrypoints/llm/test_struct_output_generate.py

@@ -4,12 +4,12 @@
 from __future__ import annotations
 
 import json
-import re
 from enum import Enum
 from typing import TYPE_CHECKING, Any
 
 import jsonschema
 import pytest
+import regex as re
 from pydantic import BaseModel
 
 from tests.reasoning.utils import run_reasoning_extraction