Add DNF support; YUM is legacy & deprecated in modern RPM-based distributions

The project currently uses `yum` as the package manager for RPM-based systems. However, `yum` has been deprecated and replaced by `dnf` (DNF5 to be more precise) in modern distributions such as Azure Linux, Fedora, Red Hat Enterprise Linux, and CentOS Stream.

Although most distributions provide a compatibility symlink (YUM->DNF), it would be beneficial for the project to officially support DNF.

Start by locating where the extension invokes yum and where RPM-based distributions are detected or handled. Trace the existing package-manager path and any related tests; done means the extension officially works with DNF, including DNF5, on the RPM-based distributions named in the issue without breaking existing support.

Written by the indexing model from the issue text.