Add __all__ to most modules beginning with 'n', 'o' and 'p' (#7345)

stdlib/pathlib.pyi

@@ -17,6 +17,8 @@ from typing_extensions import Literal
 if sys.version_info >= (3, 9):
     from types import GenericAlias
 
+__all__ = ["PurePath", "PurePosixPath", "PureWindowsPath", "Path", "PosixPath", "WindowsPath"]
+
 class PurePath(PathLike[str]):
     parts: tuple[str, ...]
     drive: str