[bg/vrf] Add support for VRF (Virtual Routing and Forwarding)
Support creating VRF interfaces through a new VRF connection type, and enslaving other interfaces to a VRF so that their routes end up in the table specified by the VRF connection.
Support creating VRF interfaces through a new VRF connection type, and enslaving other interfaces to a VRF so that their routes end up in the table specified by the VRF connection.