Add to charon test peers command ping check for charon relays

[KaloyanTanev]

🎯 Problem to be solved

We have observed on couple of occasions that charon nodes that previously had access to charon relays do not, simply the relay goes down or their round-trip time degrades. It would be good if we can test those.

🛠️ Proposed solution

• Create a relay ping test included in charon test peers command
• Create a relay ping RTT measure test included in charon test peers command