CI: update Ubuntu repositories configuration

CI: update Ubuntu repositories configuration

Recently Ubuntu updated its repositories configuration file from
`/etc/apt/sources.list` to `/etc/apt/sources.list.d/ubuntu.source`.
Thus, we need to update its location to be able to install all the
package dependencies.

In addition, the CI script was trying to uncomment the lines starting
with `deb-src`, but there is none in the new configuration file format.
Replace `Types: deb` by `Types: deb deb-src` at the beginning of the
line instead.

This commit merges all dependency installation scripts into a single
workflow, which will be called from all sites that have to install
dependencies.

Link: https://linuxconfig.org/ubuntus-repository-configuration-ubuntu-sources-have-moved-to-etc-apt-sources-list-d-ubuntu-sources
Closes: https://github.com/shadow-maint/shadow/issues/1088
Reported-by: Alejandro Colomar <alx@kernel.org>
Signed-off-by: Iker Pedrosa <ipedrosa@redhat.com>