Draft: Introduce module for Knot Resolver to store DHCP leases both v6 and v4

This is work in progress for now, it works on my machine™ as a module, but I have some permission issues and U-Bus ACL issues to solve.

I run IPv6-only network on main (I have a dual-stack network on one of WiFi APs), so didn't test DHCPv4 yet either.

Requires: build!869 (merged)