Fee control for loop outs

I've had a few loop outs get a lot more expensive than expected because they reach the conf target limit. I would love the ability to set an even greater conf target than 400 blocks or even better have more control over the RBF in the sweep transaction.

Start by tracing the loop-out flow and the sweep transaction's fee and RBF handling. Compare the requested higher confirmation target with the alternative of exposing more RBF control. Done would mean one clearly defined fee-control behavior is implemented and verified for loop-outs.

Written by the indexing model from the issue text.