chromiumos: add ChromeOS classic merge controls

We create a label and require it for submission on release branch M131,
and in the future we will require it on all future chromeos release
branches (M131+).

See: go/cros-merge-controls

Bug: 382559767
Change-Id: Id246033578ba6d5bd1e79271a7a58ea26a93d8bb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/+/6071977
Reviewed-by: Andrew Mitchell <[email protected]>
Commit-Queue: George Engelbrecht <[email protected]>
Reviewed-by: Gavin Mak <[email protected]>
2 files changed