Advertise dns ip/port to integrating apps

Apps integrating with Orbot get `SOCKS5` and `HTTP CONNECT` endpoints, but not the DNS endpoint.

The current recommendation is to forward DNS over SOCKS5 (TCP) channel, but it would be cleaner to send it to a DNS endpoint instead.

Of course Orbot lets user disable listening for DNS packets, in which case, the broadcast could return `0`s for ip/port.

https://github.com/guardianproject/orbot/blob/81d257809445fc5d9c3e32f34d5cc43f036fdaa9/orbotservice/src/main/java/org/torproject/android/service/OrbotService.java#L669

Start in orbotservice/src/main/java/org/torproject/android/service/OrbotService.java around line 669, where the existing SOCKS5 and HTTP CONNECT endpoints are advertised. Trace that broadcast and the DNS-listening state; done means integrating apps receive the DNS endpoint, or 0 for its IP and port when DNS listening is disabled.

Written by the indexing model from the issue text.