The only user of OverrideEmbedderStackStateScope is Blink where it is
used to override stack state of top-level tasks. Adjust the behavior
here to allow using this scope broadly while still supporting explicit
garbage collection calls.

Bug: chromium:1300492
Change-Id: I78c418c5f08991bf6857147cd4a537246bfcc556
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3497744Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79420}