This reverts commit ad09811a.

Reason for revert: reverted by accident

Original change's description:
> Revert "cppgc: Add DCHECK that object start bitmap is safe to use"
>
> This reverts commit 9e1db518.
>
> Reason for revert: https://chromium-review.googlesource.com/c/v8/v8/+/3535782 causes roll failures, this needs to be reverted too because it's based on it
>
> Original change's description:
> > cppgc: Add DCHECK that object start bitmap is safe to use
> >
> > During sweeeping/compaction the bitmap is being reconstructed and
> > should not be relied on for finding object start.
> > Add a DCHECK that the bitmap is fully populated.
> >
> > Bug: chromium:1307471
> > Change-Id: I4aa414722262bb6fb169123a49fce1510a60d3ef
> > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3540680
> > Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> > Commit-Queue: Omer Katz <omerkatz@chromium.org>
> > Cr-Commit-Position: refs/heads/main@{#79575}
>
> Bug: chromium:1307471
> Change-Id: I377b8737609fff33199776dce3d997f31074c59b
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3545316
> Auto-Submit: Tobias Tebbi <tebbi@google.com>
> Owners-Override: Tobias Tebbi <tebbi@google.com>
> Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Cr-Commit-Position: refs/heads/main@{#79586}

Bug: chromium:1307471
Change-Id: I04357072c6974e045c1e2bdea93d4059a1e987b2
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3545319
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Owners-Override: Tobias Tebbi <tebbi@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79592}