Build NAV package for Debian Bookworm

[lunkwill42]

We need to build a Debian Bookworm package of NAV to support the latest stable distro.

However, Debian Bookworm comes with Python 3.11, and the latest version of NAV
(5.8) does not run on Python 3.11.

From here, there are two possible strategies:

1. Wait until NAV is updated to run on Python 3.11
2. Build a bookworm package with a dependency to a Python 3.9 port for Debian Bookworm (if such a thing exists).

Getting NAV to run on Python 3.11 is a complex tree of dependency upgrades, as detailed in Uninett/nav#2788

[lunkwill42]

Removed blocked label, as the latest NAV master now supports Python 3.11 (and the default development image is now based on bookworm).

This work can now commence.