Group integration tests

[engelmi]

Please describe what you would like to see

The number of integration tests has grow quite a bit. In order to keep it manageable and lean, we should group them by, for example:

• feature
• application under test
• and/or API used (bluechictl, dbus api, systemctl, etc)

For this we can introduce new directories to group them and add tmt tags to their .fmf.