Mark a pull request as impacting all CI scopes

When a pull request changes something that affects your whole build — CI or build-system configuration, for example — you can now mark it as impacting all scopes instead of listing every target. Mergify treats such a pull request as a merge-queue barrier: it runs on its own, and everything queued after it waits for it, so a sweeping change can’t slip through a parallel lane.

Report it from CI with the scopes API (an explicit all_scopes flag alongside the usual scope list), and see it highlighted in the merge-queue view.