Payment Retries

[ConorOkus]

Add a Payment Retries section to Sending Payments.

Includes new InvoicePayer API that retires payments as paths fail.

Released v0.0.103.0
Pull Request

[jkczyz]

Looks like we also need to update both tutorials to use InvoicePayer similarly to how it's used in the sample.

lightningdevkit/ldk-sample#40

[moneyball]

Something Jeff said that I thought would be good to include in our docs:
"Just for clarification there are two things that may be getting conflated here: the scorer and the retrier. The scorer is used when finding a route and when getting events from successful and failed paths. The retrier consumes those events by telling the scorer that a path has failed or succeeded and then retries by querying for a (potentially new) path with the updated scorer. LDK users can use the LDK scorer and their own retry logic, the latter of which delegates to the scorer just as our retrier is doing."