[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/sample/utils.py

@@ -1,9 +1,10 @@
 # SPDX-License-Identifier: Apache-2.0
 
-import re
 from enum import Enum
 from typing import Optional
 
+import regex as re
+
 from vllm import CompletionOutput