Show moderation control form on diffs between latest published and current draft workflow states

If/when #2875843: Display content moderation form on published revisions → gets in, we would want this form on the additional relevant diffs analogous to the revision pages outlined there.

Made a module as a proof of concept for this, would appreciate Diff module maintainer feedback on if it should/could become part of diff:

https://www.drupal.org/project/diff_moderate →

Presently the main rough edge in my view is there cannot be a link to a diff if there has not yet been a published revision, so in those cases it falls back to linking to the latest revision, on the presumption that the Content Moderation form is enabled there as Drupal core allows and so provides an analogous experience.

Here is what it looks like in operation:

I think this is fine as a separate module