Put a little pop-up explanation on relay-search when dirport is 0 because of a recent version

Starting in Tor 0.4.6.1-alpha (tpo/core/tor#40282 (closed)), Tor relays that have a DirPort set still opt to publish a 0 in their descriptor. This is because nothing really uses that port anymore, so we're simplifying things by no longer publishing it.

But this choice still confuses relay operators, because they open the port, nyx tells them the port is working, but relay-search says it's 0:
https://lists.torproject.org/pipermail/tor-relays/2022-January/020227.html

We should put a little pop-up question-mark explainer near the DirPort entry on the relay-search page for these relays, saying something like "Tor relays running 0.4.6.1-alpha or later no longer advertise a DirPort, and that's normal, see this ticket".