Port from python3-dnf to python3-libdnf5

[yselkowitz]

As of Fedora 41, dnf5 replaces dnf as the default package manager. While the latter still exists as a library with several remaining consumers, at some point it will no longer be supported in Fedora, and therefore we need to work on migrating. This might also help performance, but ultimately needs to be done anyway.

#71 should be a prerequisite to this.

libdnf5 API docs: https://dnf5.readthedocs.io/en/latest/api/python/python.html