[tor-relays] handle malicous IPv6 systems abusing the /64 hostmask

I extended my DDoS solution [1] by blocking systems where malicous connections attempts where observed from up to 256 IPv6 addresses of the same /64 block within 24 hours from hosters providing /64 hostmasks. For now it is rather a quirk than a generic solution. But it works well. And it extends the solution to accept now manual block requests like     ipset add tor-ddos6-5443 <IPv6 address> -exist [1] https://github.com/toralf/torutils?tab=readme-ov-file#details -- Toralf