Marking holds the process wide mutex for synchronizing CrossThread*
references. In addition, marking may also create temporary copies of
Member references for concurrent tracing (snapshot).

Provide HeapRegistry with its own mutex to avoid a deadlock with
Member checking during marking.

Bug: chromium:1056170
Change-Id: I31d922ec1a476942e29d8d4fa7d864a015f428cc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2904211
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74646}