Integrate gitlab-ci/CI-fix-merges-after-gitlab-ci and 2 more

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Commit: https://gitlab.com/SECO-Northern-Europe/yocto/infrastructure/gitlab-ci/-/commit/7381d5983371f0bedd89d6c40db6c600932909e6

CI: merge_into_manifest: Fix already merged detection

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Commit: https://gitlab.com/SECO-Northern-Europe/yocto/infrastructure/gitlab-ci/-/commit/5bb84a04cd6de815350f7dbcf59dd04c2b94a6f7

CI: Merge_into_manifest: Fixes for merge detection

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Commit: https://gitlab.com/SECO-Northern-Europe/yocto/infrastructure/gitlab-ci/-/commit/285ce1951cc2ce2f6a0c390a6ece5042d930e95a

CI: Merge_into_manifest: Fixes for merge detection