And add a hook for it in the gerrit recipe_module.

This will allow invocations of gerrit_client to set votes like
"code-review-1" or "commit-queue+1" on CLs. This will be used by bots
to control CLs they just created with update_files().

Bug: 1250084
Change-Id: I888458983165fed5882e5c37cba4a69dbfb9b810
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3207266
Commit-Queue: Ben Pastene <bpastene@chromium.org>
Reviewed-by: Josip Sokcevic <sokcevic@google.com>