unify packaging tests
Currently, there are two different implementations of packaging tests:
- depend on external repos (currently OBS)
- use VMs, because we need to test systemd integration
- are pretty much exactly what the user would use
- primarily test default config
I think tests/packaging are redundant and they add additional maintenance burden (see my opinion in !947 (comment 154887)). However, they do test that all supported modules can be loaded in config. This functionality should be moved and unified with distro/tests as additional test, so we don't have to maintain two separate implementations of these tests.