Similar to the FullGC marking hierarchy (MarkingVisitorBase, with
derived classes MainMarkingVisitor and ConcurrentMarkingVisitor),
this CL introduces YoungGenerationMarkingVisitorBase +
YoungGenerationConcurrentMarkingVisitor, and refactors
YoungGenerationMarkingVisitor to inherit from
YoungGenerationMarkingVisitorBase.

YoungGenerationConcurrentMarkingVisitor dispatches to functions
refactored to ConcurrentMarkingVisitorUtility by the previous CL.

Bug: v8:13012
Change-Id: I0e827eb95732ed9ddf027fe68e25a0839cdda773
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3780524Reviewed-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@{#81976}