Convert more raw Handle<Map> uses to MapRef.

Bug: v8:7790
Change-Id: Id638b70607aa5a73404ee37dfda5e038018be525
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3067337
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Reviewed-by: Santiago Aboy Solanes <solanes@chromium.org>
Cr-Commit-Position: refs/heads/master@{#76089}