This is a reland of 4f4b4f74

Original change's description:
> cppgc-js: Add unittest for CollectCustomSpaceStatisticsAtLastGC
>
> Drive-by: fix delayed task implementation in cpp-heap.cc.
>
> Bug: chromium:1056170
> Change-Id: Ie92d909056532047b378ebfafeb98273997e60e9
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2883618
> Commit-Queue: Omer Katz <omerkatz@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#74530}

Bug: chromium:1056170
Change-Id: Ic3a7bb269e23acf728af57a9733600567659e76b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2897084
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74601}