branching: Coalesce manual OBS jobs - T8136

The current manual activities are split in several steps that cause maintainers to jump many time from the GitLab pipeline to the OBS host and back.

By reordering and coalescing we're now down to only two steps that involve jumping from gitLab to the OBS host.

In addition the jobs printing the commands to be executed manually are now started automatically and only the jobs immediately after them need to be triggered manually, considerably reducing the amount of clicking maintainers have to do.