Sweeper needs to clean up slots in the OLD_TO_SHARED remembered set
as well in the future. Unlike OLD_TO_NEW or OLD_TO_OLD this remembered
set will not be reset after a full GC. So we will have to remove from it
both during and after a full GC when sweeping.

However in the current implementation we still reset this remembered set
in a shared GC. This only works because we scan all client heaps
during a shared GC anyways to rebuild the remembered set. We will get
rid of that when all required write barriers are implemented.

Bug: v8:11708
Change-Id: Ib891a882fdf70671a483c8662408cf64e72134c6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3574546Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79874}