iwd: Register the Netconfig agent

Handle IP Configuration requests from IWD so that, when IWD's main.conf
setting [General].NetworkConfigurationEnabled is true, we don't try to
run DHCP or static addressing in parallel with IWD's internal DHCP or
static addressing.
56 jobs for iwd-netconfig in 31 minutes and 43 seconds (queued for 7 seconds)