This reverts commit 9a0e6bd5.

Reason for revert: Speculative revert for https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20-%20builder/47777

Original change's description:
> cppgc: Port concurrent sweeper
> 
> 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}

TBR=ulan@chromium.org,mlippautz@chromium.org,bikineev@chromium.org,omerkatz@chromium.org

Change-Id: I5530f11f7b8560116324bb156ba98e426c0feb35
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: chromium:1056170
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2215057Reviewed-by: Maya Lekova <mslekova@chromium.org>
Commit-Queue: Maya Lekova <mslekova@chromium.org>
Cr-Commit-Position: refs/heads/master@{#67970}