New localize DHCP server commands
The idea is to expose a new command which mimics the subnet selection returning from various parameters (e.g. IP address, interface name, client classes (guards), relay address[es], etc) the subnet (id and text) and eventually the shared network (name). Should support the 3 instances of subnet selection (v4, v6 and v4-over-v6) for not option driven cases. Related to #2878