[Shortcut] Create shortcut updater.

This CL creates the shortcut updater to handle updates of shortcuts.

BUG=1412708

Change-Id: I8c04e58d28f7400997ce4654a0952d7bc678879e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4556245


Reviewed-by: Tim Sergeant <tsergeant@chromium.org>
Auto-Submit: Maggie Cai <mxcai@chromium.org>
Commit-Queue: Tim Sergeant <tsergeant@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1149445}