Support next(iterator, default) (pytorch#159483)

Pull Request resolved: pytorch#159483
Approved by: https://github.com/mlazos
ghstack dependencies: pytorch#159365, pytorch#159366, pytorch#159368

Author: guilhermeleobas

test/dynamo_expected_failures/CPython313-test_userlist-UserListTest.test_exhausted_iterator

@@ -46,6 +46,7 @@
 from ..exc import (
     AttributeMutationError,
     ObservedAttributeError,
+    ObservedUserStopIteration,
     raise_observed_exception,
     unimplemented_v2,
     Unsupported,
@@ -2140,9 +2141,14 @@ def call_issubclass(self, tx: "InstructionTranslator", left_ty, right_ty):
     def call_super(self, tx: "InstructionTranslator", a, b):
         return variables.SuperVariable(a, b)
 
-    def call_next(self, tx: "InstructionTranslator", arg: VariableTracker):
+    def call_next(self, tx: "InstructionTranslator", *args):
+        arg = args[0]
         try:
             return arg.next_variable(tx)
+        except ObservedUserStopIteration:
+            if len(args) == 2:
+                return args[1]
+            raise
         except Unsupported as ex:
             if isinstance(arg, variables.BaseListVariable):
                 ex.remove_from_stats()