This CL renames ConcurrentMarking::JobTask to JobTaskMajor, adds
JobTaskMinor, and makes ScheduleJob branch to schedule the respective
JobTask depending on its GarbageCollector parameter.

Bug: v8:13012
Change-Id: Ic7ab15ba70f7d4e86c94a6824623c258aa8b739c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3850482Reviewed-by: Omer Katz <omerkatz@chromium.org>
Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
Commit-Queue: Leon Bettscheider <bettscheider@google.com>
Cr-Commit-Position: refs/heads/main@{#82913}