Enables python formatting in git cl format by default
for all files that have a .style.yapf file in a parent
directory up to the repository root. If no .style.yapf
file is found the --python flag still needs to be
set explicitly for python formatting to be enabled.
Also adds a --no-python to explicitly disable python
formatting on any file even if a .style.yapf file is found.

This allows default formatting to be enabled on a per
project/directory basis by adding a .style.yapf file.

Bug:846432
Change-Id: I40d899ec1a3e0dfca445e04b91befab113416175
Reviewed-on: https://chromium-review.googlesource.com/c/1316415
Commit-Queue: Aiden Benner <abenner@google.com>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>