Describe desired feature

While we have one scorer per node in SimNode, we're not actually reporting outcomes to the scorer once the payment has resolved. This should be done by importing the ScorerUpdate trait and reporting payment success/failure once we're done tracking the payment.

This will require that we:

1. Store the path that payments used so that we can report them (probably in SimNode.in_flight?)
2. Return the failing index from propagate_payment so that we can successfully report the failing channel

Use case for feature

This makes pathfinding (more) realistic.

Would you like to contribute code for this feature?

Happy to write code or review.