TASK: Switch ELN to DNF5

[yselkowitz]

What does the ELN SIG need to do?

DNF5 is now the default package manager in Fedora 41, so presumably RHEL 11 will follow suit and therefore so should ELN. In order to do so, the following step must be taken:

• %dnf5_obsoletes_dnf needs to be true for RHEL 11 in both dnf.spec and dnf5.spec simultaneously, meaning switching 0%{?rhel} > 11 to 0%{?rhel} > 10 in coordinated releases of both packages in tandem.

At the same time, presumably dnf-4, libdnf, etc. will see less maintenance, and therefore should also be dropped. However, getting rid of those will take more work, mostly beyond our scope:

• anaconda needs to be ported to python3-libdnf5
• Switch osbuild to use python3-libdnf5 instead of python3-libdnf: spec: use python3-libdnf5 in RHEL 11 and ELN osbuild/osbuild#1894
• PackageKit needs to be ported to libdnf5
• policycoreutils(-devel) needs to be ported to python3-libdnf5
• subscription-manager needs to be ported to python3-libdnf5