Integrate gitlab-ci/use-multiple-ci-test-pipelines

Commit: seco-ne/yocto/infrastructure/gitlab-ci@b20f6b95

Use multiple CI test pipelines

Instead of mixing dedicated CI test jobs and Yocto build simulation jobs within one pipeline, use the new multi-build-pipelines architecture to split them up into separate child pipelines. This also makes most of the Yocto pipeline code reusable, so that we don't have to declare all the jobs again in ci-test.