Bulk edit merge requests should support merging
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### Proposal
When clicking "Bulk edit" on a "Merge requests" page, there should simply be a button available to merge the selected merge requests ASAP. This would make automated version updates (from Renovate or the like) go from a massive chore (open up dozens of tabs, and press "Merge" in each of them) to a small handful of steps on a single page.
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