Warn relay operators when we guess an address from several equally valid alternatives
When Tor chooses an address based on local network interface addresses, warn the operator if there were several valid addresses.
#20163 (moved) makes sure that we use the OS interface order, which is hopefully:
- stable, and
- in an order determined by the operator.
It would be nice to do this if DNS returns several results as well, but I'm not sure if that's even possible. And it probably deserves a separate ticket if it is.