[3.8] bpo-27657: Fix urlparse() with numeric paths (GH-661) (#16839)

* bpo-27657: Fix urlparse() with numeric paths

Revert parsing decision from bpo-754016 in favor of the documented
consensus in bpo-16932 of how to treat strings without a // to
designate the netloc.

* bpo-22891: Remove urlsplit() optimization for 'http' prefixed inputs.
(cherry picked from commit 5a88d50ff013a64fbdb25b877c87644a9034c969)

Co-authored-by: Tim Graham <timograham@gmail.com>
3 files changed