relay: Warn about the lack of ContactInfo and the consequence

The network health team (including bad relays) as been rejecting group of relays more and more that do not have their ContactInfo or/and MyFamily set (for a group of relays from the same operator).

These are for safety and health purposes of the network. See the relay guidelines for that.

That being said, we should improve the log notice that an operator get when failing to set ContactInfo to a warning and adding a sentence that says they might get rejected from the network due to a lack of valid responsive ContactInfo.

I would argue that this needs a backport for our maintained versions. Please, let me know if not agreeing with that