Internal CI systems and the new GitHub CI system were out of sync,
with the external system not doing any linting. Further, the internal
system was using an internal-only linter for Python.
This creates a script for Python linting based on the open-source
pylint tool, checks in the Google Style Guide's pylintrc file, creates
a custom action for linting and adds it to the existing workflows,
fixes pre-existing linter errors in Python scripts, and updates pylint
overrides.
b/190743862
Change-Id: Iff1f5d4690b32479af777ded0834c31c2161bd10
56e227267c