While no scavenger thread reads the content of an object copied by
another thread, we still need memory ordering in order to read the page
flags for a forwarded object.

Change-Id: I831e9dccb03d32daf3c4847613614d26533ba825
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2944436Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74979}