better support for ldk's channel close utxo's

[johncantrell97]

currently we just automatically sweep any ldk created utxo's into our bdk wallet when a channel is closed. this works fine but it costs the user an extra transaction.

in order to remove this extra transaction we can store the utxo information to our db and present these utxo's alongside all the user's other utxo's whenever they spend.

it definitely complicates spending though, not sure if it's really worth it. seems 'ok' for case where user is doing manual utxo selection. ton of work (or maybe impossible) to perform automatic utxo selection when spending from both ldk utxos and bdk utxos.

other option is to figure out a clean way to store these IN bdk utxo database. not sure that really makes sense though because bdk db is intended to be ephemeral / fully recoverable from a chain scan -- these don't fit that model at all.