Integrate gitlab-ci/add-job-to-cancel-outdated-pipelines and 1 more

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@ea1f3bad

cancel_pipelines: include downstream pipelines

--

Commit: seco-ne/yocto/infrastructure/gitlab-ci@c8f97623

Add job to cancel outdated pipelines in merge requests

Everytime we push a new commit to a branch, a new pipeline is created.
Often the pipeline for the previous commit has not finished yet, and
GitLab does not automatically cancel it. It consumes valuable build
time, even if we don't need the results anymore.
Adding a MR pipeline job to search for previous pipelines on the same
branch and cancel them explicitly.