Make cli output json

[benthecarman]

Previously we would output the debug format of each of our return times which worked, but was not very usable. You could not easily pipe results with cli tools or anything like that. This changes the results to be output to json to make it easier to use and more similiar to what people expect.

This had one annoyance because since our structs are generated using prost, we cannot just simply add the serde traits to the structs, so instead we recreate the types we are going to output in the cli and covert them. There are a couple places where I just created "empty" default versions of types because we had to handle the None case because of how proto handles structs, not totally sure if this is the best move or if we should do something like an unreachable instead

[ldk-reviews-bot]

I've assigned @valentinewallace as a reviewer!
I'll wait for their review and will help manage the review process.
Once they submit their review, I'll check if a second reviewer would be helpful.