This CL introduces a new internal class PerIsolateAssertSwitch which
gives a static Allow/Disallow interface to be used from within classes
such as DisallowJavascriptExecutionScope without the need for slow heap
allocations.

Bug: chromium:1155348
Change-Id: I66cd8377b5d9c43510165cd7b9a7f5ccdaf45c18
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2617086
Auto-Submit: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Leszek Swirski <leszeks@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72273}