Add __orig_bases__ to TypedDict classes (#10221)

stdlib/typing_extensions.pyi

@@ -148,6 +148,7 @@ class _TypedDict(Mapping[str, object], metaclass=abc.ABCMeta):
     __required_keys__: ClassVar[frozenset[str]]
     __optional_keys__: ClassVar[frozenset[str]]
     __total__: ClassVar[bool]
+    __orig_bases__: ClassVar[tuple[Any, ...]]
     def copy(self) -> Self: ...
     # Using Never so that only calls using mypy plugin hook that specialize the signature
     # can go through.