Integrate gitlab-ci/move-sdk-to-subfolder and 1 more

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@bab6f811

Package: move SDK files to subfolder "sdk"

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@8bcaa426

scripts: Add delete_job_artifacts script to delete all artifacts from untagged jobs

For a given project all artifacts may be deleted. This was needed due to
space limitations on the gitlab server.