Preparations for the Big Reformat (#4228)

A few comments between imports were removed or moved to the top of the
import block, due to behavioral differences between black and isort. See
psf/black#251 for details.

In two instances @overloads at the top of the file needed to be moved
due to psf/black#1490.

stdlib/3/os/__init__.pyi

@@ -7,7 +7,6 @@ from typing import (
 )
 from _typeshed import AnyPath
 
-# Re-exported names from other modules.
 from builtins import OSError as error
 from . import path as path