Rework --repositories for Debian/Ubuntu to allow enabling backports, proposed, debuginfo, ...

[DaanDeMeyer]

Currently, we enable source and debug repositories by default for Debian because there's no easy way to enable them using the existing --repositories option like for arch and rpm based distributions because --repositories currently enables components on Debian/Ubuntu. We need to devise a way to allow using --repositories to enable not only components, but also extra repositories in a convenient way, to more closely match how --repositories works for the other distributions. This then allows us to disable debuginfo and source repositories by default, since they can then be easily enabled using --repositories