This reverts commit a3f66927.

Reason for revert: test failures on TSAN/no-concurrent-marking bot:
https://ci.chromium.org/ui/p/v8/builders/ci/V8%20Linux64%20TSAN%20-%20no-concurrent-marking/8549/overview

Original change's description:
> [heap] Refactor atomic marking phase
>
> The atomic marking phase was organized in many distinct smaller
> phases. In particular, before http://crrev.com/c/3584115 the marking
> phase split into two large separate phases.
>
> This CL reorganizes marking into two phases that perform regular V8
> heap marking, Oilpan, and ephemerons:
> - A parallel phase that likely drains all marking worklists;
> - A single-threaded final phase to catch any left overs;
>
> This avoids artificial splitting in phases and also avoids repeated
> starting and joining of jobs.
>
> Change-Id: I5cccfc5777837d9ece10d8f4925781bf2d07d9da
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3602507
> Reviewed-by: Omer Katz <omerkatz@chromium.org>
> Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
> Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#80265}

Change-Id: I4838e9316bd30f8a0b78fa6a27820d3457e1e579
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3614972
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Adam Klein <adamk@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80267}