Integrate gitlab-ci/share-manifest-pipeline and 2 more

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@9b8cf51c

Share manifest pipeline for ci-test and yocto

Combine all common yaml parts in manifest-pipeline.yml and add
manifest-pipeline-yocto.yml and manifest-pipeline-ci-test.yml
containing the different variable assignments for each environment.

This change implicitly introduces parent-child build job generation in
the ci-test pipeline, like it is done in the yocto pipeline already.
The ci-test build jobs have been moved to build-jobs-ci-test.jinja2
accordingly.

Furthermore rename GITLAB_CI_CURRENT_REV to GITLAB_CI_REVISION and
remove the run conditions from all generated build jobs, since these are
already present in the upstream trigger job.

The repos including these files have to be updated with the new file
and variable names.

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@c1b939fe

Use CI variables in build template directly

The job generation script implicitly passes the OS environment to the
template, so that the template has access to all GitLab CI variables.
Hence there is no need to explicitly pass any of them as command line
arguments.

This change makes the "generate-build-jobs" job more generic, so that
it can be shared with the ci-test pipeline in the future.

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Commit: seco-ne/yocto/infrastructure/gitlab-ci@775c09c1

Add gitlab_backup script to download all project exports of a gitlab group