Changes

OBS: build_srcpkg: install rebar3 without apt

Avoid pulling in 600 MB of GUI dependencies.

Related: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1083096
Change-Id: I9a51df03ac173118c35d501bd21c6d023a436844

OBS: set default distro to debian 13

Change the distribution that is used to build the source packages to
debian 13 so we are on the latest one again.

Change-Id: I7c1dcca90e46645a497fd547ce1243b414c53201

OBS: support building pyhss

Build source packages for the python project pyhss similar to how we do
it for erlang projects: by downloading all dependencies ahead of time
and vendoring them in the source package.

Related: SYS#6819
Change-Id: I321090e811f7c5c142bf973c616d83cd5b2219ab

OBS: configure Osmocom pyhss fork

Add the Osmocom fork of PyHSS to scripts/obs/lib/config.py, so the
Osmocom_OBS_* jobs build source packages for it and push them to our OBS
where binary packages get built. We need to use a fork for now, as the
official repository can't run outside of a git tree yet and doesn't have
debian packaging. These changes are being upstreamed, the goal is that
we don't need to use our fork in the long run.

Related: SYS#6819
Change-Id: I8fc7ef9dc242248770711da2893492fae8a84522