Export debian:suite collections as APT repositories even if they are not in a debian:archive collection

The initial design required debian:suite collections to be part of a debian:archive collections, it made sense but in practice it's rather cumbersome as it's an extra step that does not bring any value when you don't have cross-suite constraints to ensure. And we have don't have any command to perform it!

The suggestion is thus to make all debian:suite visible by default as proper APT repositories. Optionally we could add an "exported" boolean in the data dictionary of the debian:suite collection to control whether a given suite is to be considered visible and whether metadata have to be generated for the suite.

• Rework the views in debusine/web/archives/views.py
• Modify the update_suites workflow