1) Cast to PagedSpaceBase instead of PagedSpace in sweeper.cc
2) Free LAB before filling space in heap-utils.cc

Bug: v8:12612
Change-Id: I5820c2d2f4ab832a4b5a829fc55973d93296ec10
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3892690
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Auto-Submit: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#83168}