Draft: Don't report skipped content as being missing

as it's an intentional choice of the loader not to load them, this is outside the scope of checkers to report them.

(this won't pass tests because the method doesn't actually exist, but this was in my git stash for a while and I don't want to forget about it)

Jenkins job DSCRUB/gitlab-builds #132 failed .
See Console Output and Coverage Report for more details.

added mr-reviewed-winter-2024 label

changed milestone to %Regularly scrub journal, storage, and objstorage [Roadmap - Preserve]

Unfortunately the storage API change isn't hiding in another git stash

We consider that this change isn't very high priority as we have many more issues with the "reference checking" side of the scrubber, which would need a more global analysis. skipped contents are, after all, a pretty fringe edge case.