Show in MR widget if the merge was reverted
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Example: https://gitlab.com/gitlab-org/gitlab_git/merge_requests/65 was reverted by https://gitlab.com/gitlab-org/gitlab_git/commit/12f23c3a758210e936234e5cb724df6242bd5f0e, which it knows because it doesn't show the `Revert` button.
It would be nice if it stated outright "The merge commit was reverted by Douwe Maan in [SHA] 10 minutes ago". Could also be shown on an individual commit page.
### Design

issue