* DHCP: switch "internal" DHCPv4 plugin from code based on systemd to use nettools' n-dhcp4 library. * Add support for "scope" attribute for IPv4 routes. * Add support for specifying IAID and FQDN flags for DHCP request. * Add a '802-1x.optional' property to consider the wired 802.1X authentication as optional. * Use the Network Cost Wi-Fi information element to determine metered device state.