This class is only used for heap verification and doesn't need to be
public.

Bug: v8:11708
Change-Id: I9d1750a6f701ed0d9a106f8d93ab3ff82bbf4f3b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3862208Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Dominik Inführ <dinfuehr@chromium.org>
Cr-Commit-Position: refs/heads/main@{#82814}