This reverts commit aba185a7.

Reason for revert: We want to keep this API.

Original change's description:
> [heap] Remove slots when shrinking objects
>
> Immediately remove recorded old-to-new slots when shrinking objects.
> This operation needs to drain the store buffer, however the store buffer
> is supposed to be removed anyway.
>
> Also do not remove slots when left-trimming since this isn't needed for
> correctness.
>
> Bug: v8:9454
> Change-Id: I751baf2dcd03c87aee9cb1ebd168e05bf373a738
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1762012
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#63271}

TBR=ulan@chromium.org,dinfuehr@chromium.org


Bug: v8:9454
Change-Id: I9524a7448cc49948915fdccc5a6b1aa22e4de4a9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1762524Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63342}