- Fix an issue where weak containers would not be marked properly when
  running with full object names. The problem was that in this
  configuration the object graph was not traversed at all in the first
  phase, meaning that no weak links would be found.
- Add edges to weak containers in the second phase that actually builds
  the snapshot.
- Mark all weak containers instead of just ephemerons, to avoid having
  fully weak containers show up as retainers.

Bug: chromium:1056170
Change-Id: I8b29e00a5d77028892c16e3c29258cd598083082
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2951730
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75081}