This reverts commit b1c3ca2a.

Reason for revert: TSan issues: https://ci.chromium.org/p/v8/builders/ci/V8%20Linux64%20TSAN/28147

Original change's description:
> [heap] Reschedule concurrent marking tasks earlier
> 
> Currently we reschedule concurrent marking tasks if all tasks finish.
> This is too conservative and we can improve performance by rescheduling
> finished tasks without waiting for all other tasks.
> 
> As a drive-by this also changes task_count_ to total_task_count_.
> 
> Change-Id: If0b3bd45ce6d52f6bcd0065dd8d3efe9ea84184a
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1789142
> Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
> Reviewed-by: Omer Katz <omerkatz@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#63593}

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

Change-Id: I5e6b406a021c8fd4834e346e02388552ee3e0036
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1789287Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63594}