This reverts commit 164a040a.

Reason for revert: roll failure: https://ci.chromium.org/ui/p/chromium/builders/try/cast_shell_linux/1164753/overview

Original change's description:
> cppgc: Add regression test and check for object start bitmap
>
> Access to the object start bitmap is only safe during marking until
> sweeping is started as the concurrent sweeper may clear and rebuild
> the bitmap at any time during sweeping.
>
> Adds a DCHECK and an additional test for a previously broken
> pre-finalizer scenario.
>
> Bug: chromium:1307471
> Change-Id: If67ade43f7cdad6de4720c0efeac11bfe8c22b3c
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3535782
> Reviewed-by: Nikolaos Papaspyrou <nikolaos@chromium.org>
> Reviewed-by: Omer Katz <omerkatz@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#79550}

Bug: chromium:1307471
Change-Id: I181e63a34eae9369184fb86112bc64e53b8bfad5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3545317
Owners-Override: Tobias Tebbi <tebbi@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79590}