Slyghtning

@coderabbitai review

~There are some LSP heuristic improvements that are still pending. I will ping the reviewers once they are pushed.~ For reviewers @bitromortac, @ProofOfKeags and @JssDWt, the LSP heuristic and fee...

@bitromortac, @ProofOfKeags, @champo thanks for your thorough reviews. I think I addressed all comments. I am still working on the probing timeout test, but imo the review can continue without...

Thanks for the review @bitromortac! I get your concern about being flexible with adaptations to the estimation if new requirements like bolt12 come in, without having to come up with...

Once again thanks for the thorough review @ProofOfKeags + @bitromortac, I've addressed all your comments. Most notably I restructured `isLsp` to only check what its name implies, and added `prepareLspRouteHints`...

Once again thank you @bitromortac for this thorough review journey. The handling of route hints by `lnd` has been especially insightful for me.

@saubyk, @Roasbeef I'd like to pick up the `OpenChannel` part if possible. Have started to explore changes in `lncli`, `rpcserver` and funding reservation. I think I can submit a draft...

I've assigned this to me as I'd like to work on the utxo selection for `SendCoin` next. cc @saubyk

As discussed offline with @Chinwendu20 we currently pursue the following high-level approach to bring manual coin selection support to `SendCoins`: 1. Add `cli` capabilities for `lncli sendcoins --utxo bc1p... --utxo...

> First pass done, I think this is almost there - great work. Just think the style of the PR needs some work. I think the style changes should either...