Remove finalization step of incremental marking. The step was
historically used to process embedder/weak work on the main thread
before invoking the atomic pause. Remove the infrastructure as the
step is not needed anymore and actually required a safepoint.

Change-Id: I208767bbac3d9a06a0b3c67aa9779f8a5fa07328
Bug: v8:12775
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3702801
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81234}