AdvanceWithDeadline() was only used from AdvanceFromTask(). So we can
move this method into AdvanceFromTask().

AdvanceFromTask() and AdvanceOnAllocation() share quite some code,
there is already a common bottleneck for both methods: Step(). So we
can move that code into Step().

Bug: v8:12775
Change-Id: I0f749f52df05d951f4310f05ff0d3977c6b2a9aa
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3843143
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82614}