Expose full payment retry strategy via Config

[benthecarman]

Replace the payment_retry_timeout_secs field with a PaymentRetryStrategyenum that mirrors LDK's Retry type, allowing users to choose between timeout-based and attempt-count-based retry strategies. Defaults to a 10-second timeout to preserve existing behavior.

This was something I needed when getting ldk-server working with loop.

[ldk-reviews-bot]

👋 Thanks for assigning @tankyleo 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.

[tnull]

An alternative would be to expose the Retry completely to allow for attempts based version as well. However, the timeout is generally simpler and more in line with what people expect.

If we do it, I'd lean towards exposing retry_strategy: Retry in the config. Should be even pretty easy to handle in bindings, as uniffi should now expose tuple enum variants.

[benthecarman]

If we do it, I'd lean towards exposing retry_strategy: Retry in the config. Should be even pretty easy to handle in bindings, as uniffi should now expose tuple enum variants.

done