When performing full GC on a shared space isolate, the GC also needs
to visit OLD_TO_SHARED slots in client isolates and update pointers.

Bug: v8:13267
Change-Id: Ida48c666dce8f5ed703a6920ad007add9235d64a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3913347
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83421}