net-mgmt/rs-aggregate: Add new port

Takes a list of IPv4 and IPv6 prefixes in conventional format on stdin, and
performs optimisations to reduce the length of the prefix list. A drop-in
replacement for the Python application aggregate6. This implementation is
upwards of 100 times faster.

PR: 274838
Reported by: Marcel Bischoff <marcel@herrbischoff.com>