Related to: https://github.com/theforeman/foreman_discovery/pull/545

We need to be able to validate whether user sourced IP set in the form is included in the available subnet.
Initially we just ran `.include?` on a Range object generated through `subnet_range` method, however, this is extremely inefficient when used on huge subnets (specifically in this case, an IPv6 range inclusion check timed out).

This brought `IPAddr#include` to the spotlight.