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.