Add retry for flaky tests in CI (#4755)

test/lang/test_choices.py

@@ -7,6 +7,7 @@ from sglang.lang.choices import (
     token_length_normalized,
     unconditional_likelihood_normalized,
 )
+from sglang.test.test_utils import CustomTestCase
 
 MOCK_CHOICES_INPUT_DATA = {
     "choices": [
@@ -51,7 +52,7 @@ MOCK_CHOICES_INPUT_DATA = {
 }
 
 
-class TestChoices(unittest.TestCase):
+class TestChoices(CustomTestCase):
 
     def test_token_length_normalized(self):
         """Confirm 'antidisestablishmentarianism' is selected due to high confidences for