Missing DEB822 .sources file support for apt::ppa

[logansymons]

Use Case

On Ubuntu 24.04, using apt::ppa, PPA .sources entries will be recreated in /etc/apt/sources.list.d on every Puppet run.
This is due to apt::ppa not having awareness of .sources files. The current situation is roughly as follows:

1. apt::ppa looks to the apt_sources fact for the relevant .list file of the PPA and doesn't find it
2. apt::ppa calls add-apt-repository to add the PPA, which is added as a .sources file
3. Go back to 1. for following Puppet run

Describe the Solution You Would Like

1. The apt_sources fact would need to recognise .sources files, not just .list files
2. apt::ppa would need to recognise .sources entries from the apt_sources fact as evidence of a PPA already being added

Describe Alternatives You've Considered

Letting .sources entries be recreated on every Puppet run is still a workable option in the meantime.

[logansymons]

Taken care of in #1169

Closing.