Schedule is simpler compared to the schedule in blink since it now
returns deadlines based on marked bytes instead of time.

If marking is ahead of schedule, return the minimum step size.
Otherwise, set step size to catch up to schedule (ignoring the time
passed while performing the step).
No more default initial step size (needed in blink since marking speed
was unknown).
If estimated schedule is exceeded (marking takes longer than 500ms), the
steps will try to mark all remaining objects but would still be capped
by the maximum step duration of 2ms.

Bug: chromium:1056170
Change-Id: I09857db161c621a12d064f9c8c21b646c34f9d71
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2375200
Commit-Queue: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Cr-Commit-Position: refs/heads/master@{#69602}