This is a reland of b1c3ca2a

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}

Change-Id: Id18bbb3cab85cd38bb7d2f21611825252ed4a1dc
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1789288Reviewed-by: Omer Katz <omerkatz@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63610}