This is a reland of 360c7afc

Changes since revert:
  - Read the unregister token using a relaxed read during marking

Original change's description:
> [weakrefs] Clear unregister token-related fields when clearing weak cells
>
> Bug: chromium:1213770
> Change-Id: Ic063e79bfa8f3dabdd29d1cc9ed74c7af44d0c31
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2923294
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Commit-Queue: Shu-yu Guo <syg@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74890}

Bug: chromium:1213770
Change-Id: I8d0b946359b85a4760113e26dbaeaa9479e3b5fd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2930554Reviewed-by: Shu-yu Guo <syg@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74925}