reinstall: Support installing podman

[cgwalters]

I'd like to allow distro images like Fedora Cloud to add system-reinstall-bootc but not necessarily pull in podman if they weren't already.

So basically:

• Change to just Recommends: podman for system-reinstall-podman
• Change the code to install it if not present (this of course raises the "package system abstraction" problem)

[vrothberg]

Thanks! Yes, that sounds like the right solution to cover the two scenarios of podman being (not) installed.

this of course raises the "package system abstraction" problem

Let's start with dnf-only systems. In the future, we can make it conditional. Other distros could still use the tool but with a hard dependency on podman.