When starting a global safepoint, it could happen that one isolate is
waiting/blocking in the event loop, which prevents this isolate from
reaching a safepoint. As a consequence we therefore deadlock when
performing the safepoint. We can solve this by simply posting a task
for each isolate that when run performs a safepoint check.

This CL also renames IncludeMainThreadUnlessInitiator to
ShouldIncludeMainThread.

Bug: v8:11708, v8:12645
Change-Id: Ide956b3c39b350c2bb0279a7dd94ff79cb9d771b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3555771Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79675}