This moves concurrent and incremental sweeping from Blink. This also
adds TestPlatform that makes it easier to test concurrent and
incremental sweeping.

Drive-by: fix unmarking of large pages.

Bug: chromium:1056170
Change-Id: Ifd50ff67b9df17ff117a5f4d4eb5a2937d3023be
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2207132
Commit-Queue: Anton Bikineev <bikineev@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67969}