Private address warning on public network too quiet

In #40208 (closed) the behaviour for when a relay doesn't publish due to an RFC1918 IP address is addressed, but in the initial report there is this line:

*\[info\] address_can_be_used(): Address '127.0.0.1' is a private IP address. Tor relays that use the default DirAuthorities must have public IP addresses.*

which is only logged at info but is the only thing that provides a hint why the relay stopped publishing. It should probably be louder and explain both ways to fix the issue.