Integrate gitlab-ci/improve-debug-output and 3 more

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@c657f31f

mirror_mr_pipeline: improve debug output

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@473f12b1

mirror_mr_pipeline: add main call

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@88708b64

Convert CRLF to LF

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@169b2fa7

Improve mirroring MR pipeline

Refactor three scripts into one in order to support triggering a new
pipeline in the case of a skipped MR pipeline. This was not possible to
implement with the previous three-script design. The single scripts
were not used in other places anyway.