mkosi: Ensure we build all features/components in mkosi
    
    Explicitly enable all features/components in the mkosi build to
    ensure they all get built and we get an error if they can't be built.
    
    We also rework the packages sections of all mkosi configs to reduce
    duplication and cover all the dependencies necessary to build/use all
    systemd features.
    
    Note that for the final image, since systemd is installed by default
    in base images, we rely on that to install the base library dependencies
    and we only list extra optional dependencies and tools that aren't already
    installed by default into the base image.
    
    We also drop the centos stream 8 mkosi build as dependencies on that
    distro are too out-of-date to be able to build all systemd features.
    Since centos stream 9 has been out for a while, let's focus on that
    and leave it to downstream to keep systemd building on centos stream 8.
    
    Finally, there's a few additions to the mkosi scripts to make sure
    services don't start by default on boot.