[Birch] Add Command Line Flag to Show Release Notes Glanceable.

Bug: b/304284590
Change-Id: I7c8cbe8de5394417dd97afb5facc674c930051df
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5397950


Auto-Submit: Owen Zhang <owenzhang@google.com>
Reviewed-by: Toni Barzic <tbarzic@chromium.org>
Commit-Queue: Owen Zhang <owenzhang@google.com>
Reviewed-by: Matthew Mourgos <mmourgos@chromium.org>
Commit-Queue: Matthew Mourgos <mmourgos@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1279962}