multi: modify sweeper.CreateSweepTx to accept conf target, style changes

In this commit, we modify the newly introduced UtxoSweeper.CreateSweepTx
to accept the confirmation target as a param of the method rather than a
struct level variable. We do this as this allows each caller to decide
at sweep time, what the fee rate should be, rather than using a global
value that is meant to work in all scenarios. For example, anytime
we're sweeping an output with a CLTV lock that's has a dependant
transaction we need to sweep/cancel, we may require a higher fee rate
than a regular force close with a CSV output.

utxonursery.go

@@ -4,11 +4,12 @@ import (
 	"bytes"
 	"encoding/binary"
 	"fmt"
-	"github.com/lightningnetwork/lnd/sweep"
 	"io"
 	"sync"
 	"sync/atomic"
 
+	"github.com/lightningnetwork/lnd/sweep"
+
 	"github.com/btcsuite/btcd/txscript"
 	"github.com/btcsuite/btcd/wire"
 	"github.com/btcsuite/btcutil"
@@ -182,6 +183,10 @@ type NurseryConfig struct {
 	// determining outputs in the chain as confirmed.
 	ConfDepth uint32
 
+	// SweepTxConfTarget assigns a confirmation target for sweep txes on
+	// which the fee calculation will be based.
+	SweepTxConfTarget uint32
+
 	// FetchClosedChannels provides access to a user's channels, such that
 	// they can be marked fully closed after incubation has concluded.
 	FetchClosedChannels func(pendingOnly bool) (
@@ -871,15 +876,15 @@ func (u *utxoNursery) graduateClass(classHeight uint32) error {
 		// generated a sweep txn for this height. Generate one if there
 		// are kindergarten outputs or cltv crib outputs to be spent.
 		if len(kgtnOutputs) > 0 {
-			sweepInputs := make([]sweep.Input,
-				len(kgtnOutputs))
+			sweepInputs := make([]sweep.Input, len(kgtnOutputs))
 			for i := range kgtnOutputs {
 				sweepInputs[i] = &kgtnOutputs[i]
 			}
 
 			finalTx, err = u.cfg.Sweeper.CreateSweepTx(
-				sweepInputs, classHeight)
-
+				sweepInputs, u.cfg.SweepTxConfTarget,
+				classHeight,
+			)
 			if err != nil {
 				utxnLog.Errorf("Failed to create sweep txn at "+
 					"height=%d", classHeight)