Previously, an allocation from a separate thread could grab the
just-released region and make it accessible before the regions
permissions are changed to kNoAccess at the end of ReleasePages.

Bug: v8:12414
Change-Id: I98c8f8e3df76d4a44c357ddab107cfeff20049b8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3293083Reviewed-by: Igor Sheludko <ishell@chromium.org>
Commit-Queue: Samuel Groß <saelo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#77997}