Prop 311: 6.1. Test IPv6 ORPort Reachability on the Tor Network

Test the IPv6 ORPort Reachability and Extends changes in proposal 311, on the public tor network, with a small number of relays and bridges.

We can do public tests after each major feature is merged. We can also wait for multiple features to merge, and test them all.

Here are some useful features that we can test:

legacy/trac#33222 (moved) / legacy/trac#33226 (moved) IPv6 ORPort Reachability Self-Tests / Relay=3 Protocol legacy/trac#33223 (moved) Don't Publish Descriptor if IPv6 ORPort is Unreachable

See proposal 311, section 6.1, initial public test part: ​https://gitweb.torproject.org/torspec.git/tree/proposals/311-relay-ipv6-reachability.txt#n671