setuptools&distutils: setup returns a Distribution (#11617)

`setup` returns a `Distribution`

stdlib/distutils/core.pyi

@@ -53,5 +53,5 @@ def setup(
     password: str = ...,
     fullname: str = ...,
     **attrs: Any,
-) -> None: ...
+) -> Distribution: ...
 def run_setup(script_name: str, script_args: list[str] | None = None, stop_after: str = "run") -> Distribution: ...