lampo backend interface re-thinking

[vincenzopalazzo]

I had a conversation with @tnull, (an expert in LDK and Lightning), who was kind enough to review my initial of lampo. It is a little bit hacky had buggy but I am not surprised by the code that I wrote on some hot London night in 2022.

The main issue is that the lampo-bitcoind has several bugs events that ldk can take in the wrong way. I need to think about potential solutions and all the bugs, and one possibility might be found here: https://docs.rs/lightning-transaction-sync/latest/lightning_transaction_sync/#usage-example.

I'm uncertain about how to handle the lampo-nakamoto backend. However, it's clear that incorporating lightning_transaction_sync is important for moving towards a well-tested solution and OFC the important part for me is that it is maintained by ldk people 😄. However, we'll need to consider if this allows us the same level of flexibility.