This is a reland of 3df36990

Original change's description:
> cppgc: Port ObjectStartBitmap
> 
> This ports ObjectStartBitmap from Blink.
> 
> Bug: chromium:1056170
> Change-Id: Ib959d9ac1c5e1e34ffa6418f77956e993c570ffc
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2181331
> Commit-Queue: Anton Bikineev <bikineev@chromium.org>
> Reviewed-by: Omer Katz <omerkatz@chromium.org>
> Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
> Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#67735}

Bug: chromium:1056170
Change-Id: I6e2fd99e96bebe3060f4feb8503ab04c0d452d51
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2198986Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67772}