Draft: packaging-check-installability: Run dose-distcheck on APT repositories

Check the dependencies of the packages published in the APT repositories to verify there's no dependency issue preventing them to be installed.

This adds a separate report page where the installbility errors are grouped by the actual package (usually a transitive dependency) which is actually uninstallable. This shows which packages are broken for the same reason, and points to the package to fix if the broken packages should be installable.

Ignored errors are also shown as notes in the installability report, providing a way to review the effects of the ignore rules.

Rendered: https://em.pages.apertis.org/dashboard/