[arch-projects] [netcfg] Rethink systemd integration v2

[Thomas Bächler]

For net-auto-wired and -wireless, a new @-unit has to be instantiated
with the interface name. Static profiles are enabled automatically
when listed in /etc/conf.d/network NETWORKS= - the old netcfg.service
has thus been removed.

This breaks the NETWORKS=(last) functionality, and I don't think we
can handle it properly right now. NETWORKS=(menu) could never work
with systemd anyway.

I'd really like to remove netcfg at .service, net-auto-wired.service and
net-auto-wireless.service at some point, but that will break existing
setups. I don't know if we should go ahead with this.

What we should definitely do is change netcfg, wifi-menu and netcfg-menu
to use systemctl to start profiles when called manually. This would
ensure systemd can track the profiles properly, knows how to shut them
down and can track their processes.