On the initial commit of this feature, IPs were just matched with a
very simple regex that prioritised simplicity/readability over
accuracy.
This commit adds a postprocessor for ip matches that makes use of
Python's `ipaddress` in the standard library to validate all the IP
matches.
This way we don't need huge and complex regex patterns to match _and_
validate the IPs, and we can just use `ipaddress` to abstract us from
implementing all the validation logic into the regex pattern.
10533c3eba