These mutex guards may trigger GC on the slow paths; to detect misuse
(creating these guards inside GC-disallowed scopes) more reliably,
this CL adds

 DCHECK(AllowGarbageCollection::IsAllowed())

to the guard constructors.

Bug: v8:12012
Change-Id: If59514c97ba6cc9bbca3b56559bf2496cafc78d9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3043952Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75861}