Add an option to always use relays

[link2xt]

Together with #2901 it should be possible to establish all connections via proxy and not reveal the IP address even if communicating to unknown relays.

Some users may want to use P2P features of the app (calls, webxdc realtime) but never reveal the IP address.

[zh522130]

Together with #2901 it should be possible to establish all connections via proxy and not reveal the IP address even if communicating to unknown relays.

Some users may want to use P2P features of the app (calls, webxdc realtime) but never reveal the IP address.

I also need this feature. I've found that direct connections between different network operators sometimes have higher latency than using a relay.