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MB configs for Linux PGO builders.
Adding MB configs for beta and stable trybots for PGO linux as well.

Bug: 1105530
Change-Id: Ie4f01a244abfd5cd9e89fe583e7acb8706ef99cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2307633Reviewed-by: Garrett Beaty <gbeaty@chromium.org>
Commit-Queue: Jeff Yoon <jeffyoon@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790666}