Silverblue/Kinoite/Sericea/Onyx: Use unified core mode
    
    rpm-ostree is moving to unified core composes and this is now working
    for Silverblue, Kinoite, Sericea and Onyx.
    
    Requires: https://pagure.io/pungi/pull-request/1626
    Requires: https://pagure.io/workstation-ostree-config/pull-request/246
    See: https://github.com/coreos/rpm-ostree/issues/729
    See: https://fedoraproject.org/wiki/Changes/FedoraSilverblueUnifiedCore
    Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2150984
    
    Revert "Revert "Use unified core mode for Silverblue & Kinoite""
    
    See: https://pagure.io/pungi-fedora/pull-request/1115
    See: https://pagure.io/pungi-fedora/pull-request/1136
    
    This reverts commit dd54ad9f33099d795bf5501ef5704c197bb1d456.
    
    Signed-off-by: Timothée Ravier tim@siosm.fr