Also shuffle HeapType helper functionality a bit

Bug: chromium:1101629, v8:7748
Change-Id: I7c27dc96f02173c73dbac7b518e7936e4e0d5bf3
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2275965Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68659}