Allow CrossThreadPersistent and its weak form to access ASAN poisoned
memory from the GC entry points.

In general, payloads of to-be-finalized objects are poisoned until the
finalizer actually runs to avoid accidentally touching that payload.

In the case of cross-thread handles, these may need to be cleared by a
different thread before the finalizer actually runs. In order to clear
those references, the slot needs to be unpoisoned.

This is issue is ASAN-only and does not affect production or other
debug builds.

Bug: chromium:1230599, chromium:1056170
Change-Id: If4d0808953047319b02653821abbb5c638084dc5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3040845
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75846}