presets: Use a commmon desktop preset and spin specific ones
    
    Split the 80-workstation.preset into a 81-desktop.preset with presets
    common to all Fedora desktop variants and keeps the varaint specific
    changes in separated preset files: 80-workstation.preset &
    80-kde.preset.
    
    This change is a NOP for Workstation and Silverblue.
    This change disables sshd by defaut and switches cups to the socket unit
    for the KDE Spin and Kinoite.
    
    See: https://pagure.io/fedora-kde/SIG/issue/126