[Relay] Warn about the risk of ending up on blocklists

Some relay operators running non-exits on their residential connections are having a bad time with blocklists. This isn't a new thing. In the tor-relays mailing list and the Tor Forum, we've been asking relay operators to avoid running public nodes on their residential connections, for example, running a Snowflake proxy or a bridge will avoid your IP ending up on blocklists.