Add type loopOutSweepFeerateProvider which determines confTarget based on
distance to swap expiration, then determines feerate and fee using. Fee rate
is plugged into sweepbatcher using WithCustomFeeRate. Option WithPublishDelay
is used to make sure fee-rate is updated by loopout.go before the value is used
by sweepbatcher.
When determining confTarget, there are few adjustments over raw distance to
cltv_expiry:
- make sure confTarget is positive (if the swap has expired, raw distance is
negative)
- If confTarget is less than or equal to DefaultSweepConfTargetDelta (10),
cap it with urgentSweepConfTarget and apply fee factor (1.1x).
Also, if feerate is less than floor (1 sat/vbyte), then the floor is used.
DefaultSweepConfTargetDelta was decreased from 18 to 10.
Every block 100 sats/kw fee bump is disabled. Sweepbatcher re-targets feerate
every block according to current mempool conditions and the number of blocks
until expiry.
Added tests for loopOutSweepFeerateProvider simulating various conditions.
