Add codeobject.co_positions() for Python 3.11 (#6339)

Author: lancelote

stdlib/types.pyi

@@ -144,6 +144,8 @@ class CodeType:
             co_name: str = ...,
             co_lnotab: bytes = ...,
         ) -> CodeType: ...
+    if sys.version_info >= (3, 11):
+        def co_positions(self) -> Iterable[tuple[int | None, int | None, int | None, int | None]]: ...
 
 @final
 class MappingProxyType(Mapping[_KT, _VT_co], Generic[_KT, _VT_co]):