The check whether worklists are empty sits after marking the
transitive closure, when it is guaranteed that no concurrent marker is
running anymore.

Bug: chromium:1325628
Change-Id: Ibfa7278df2181a0aa6c7e0f1d53d51e8afaa3352
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3647830
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80566}