Introduce common bottleneck for all incremental marking step
invocations from a task context. This will later be used to move
code out of IncrementalMarking::Step.

Bug: v8:11708
Change-Id: Iba2dc2402083f8b4152ded56eaf0e13d473442a8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3822682Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82343}