ci: migrate to github merge queues [backport 2023.10] · RIOT-OS/RIOT@5bde3d2

Commit message is longer than 50 (but < 72) characters: ".github/workflows/*: Allow merge_groups and prs to be required"

Commit message is longer than 50 (but < 72) characters: ".murdock: clarify `is_merge_queue_build()` help text"

Commit message is longer than 50 (but < 72) characters: "ci: workflows: static-test: fix CI_BASE_BRANCH for merge_groups"