Add nrepl message logging

[bpringe]

This has been discussed before, and I believe Cider has this. It could help us debug some issues, such as #1153, but probably several others.

I think an output channel would be good for this. What do you think @PEZ?

[bpringe]

This is the feature in Cider: https://docs.cider.mx/cider/1.1/troubleshooting.html#debugging-the-communication-with-nrepl

[ieugen]

I would also like to see this. Working on a nrepl ssh transport and debugging the messages sent between client and server would come in handy.