When objects are recorded for conservative handling and the GC is
finalized conservatively, with a different stack, we rely on
MarkNotFullyConstructedObjects(). In this method, the objects are
initially marked, only to be forwarded to handlers that try to mark
them again.

Bug: chromium:1056170
Change-Id: I942e7b0ec88aae08e3fe06b7cb3ff4a86dc42f36
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2744074
Auto-Submit: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73281}