Tidy up OnionPerf DNS records
It seems that DNS records still exist for old OnionPerf hosts, which might even now be pointing at hosts that we don't own.
To start off, let's get a list of the current records under *.onionperf.torproject.net and then @acute can confirm which are real and which no longer exist.
We should also check that none of the IP addresses are pointing at places we don't control, and if so we should check the TLS certificate transparency logs to make sure no certificates have been issued for those domain names. It's unlikely but you never know.