Mark objects as grey when pushing to worklist and mark as black when
objects are visited.

Bug: v8:12612
Change-Id: I5ad28c4481052f41588f43dc39dd44f132a27dfb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3810467
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82290}