Via INSTALLER-4183 we agreed to remove modularization support going forward.

As the change approved we can merge the DNF5 support and that change effectively will make modularity unsupported in the installer (we don't have support for it in DNF5 integration).

This task is tracking the clean-up of remaining pieces:

• Remove "module" command and code which implements it in kickstart
• Clean-up module command from kickstart documentation
• Remove modularity-related tests from kickstart tests