GitLab

- chromium_trybot recipe set in ci.star for both bots
- mb configs set in mb_config.pyl for both bots, exactly the same
  as the builders

Bug: 1055164,912681
Change-Id: Ib2235e9803ddafddbd7fc44be493ab06fcb74c01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2121429
Commit-Queue: Jeff Yoon <jeffyoon@chromium.org>
Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Cr-Commit-Position: refs/heads/master@{#756442}