chainfee: create new chainfee package extracting fees from lnwallet

In this commit, we create a new chainfee package, that houses all fee
related functionality used within the codebase. The creation of this new
package furthers our long-term goal of extracting functionality from the
bloated `lnwallet` package into new distinct packages. Additionally,
this new packages resolves a class of import cycle that could arise if a
new package that was imported by something in `lnwallet` wanted to use
the existing fee related functions in the prior `lnwallet` package.

rpcserver.go

@@ -44,6 +44,7 @@ import (
 	"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
 	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet"
+	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwire"
 	"github.com/lightningnetwork/lnd/macaroons"
 	"github.com/lightningnetwork/lnd/monitoring"
@@ -815,7 +816,7 @@ func addrPairsToOutputs(addrPairs map[string]int64) ([]*wire.TxOut, error) {
 // more addresses specified in the passed payment map. The payment map maps an
 // address to a specified output value to be sent to that address.
 func (r *rpcServer) sendCoinsOnChain(paymentMap map[string]int64,
-	feeRate lnwallet.SatPerKWeight) (*chainhash.Hash, error) {
+	feeRate chainfee.SatPerKWeight) (*chainhash.Hash, error) {
 
 	outputs, err := addrPairsToOutputs(paymentMap)
 	if err != nil {
@@ -1000,7 +1001,7 @@ func (r *rpcServer) SendCoins(ctx context.Context,
 
 	// Based on the passed fee related parameters, we'll determine an
 	// appropriate fee rate for this transaction.
-	satPerKw := lnwallet.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
+	satPerKw := chainfee.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
 	feePerKw, err := sweep.DetermineFeePerKw(
 		r.server.cc.feeEstimator, sweep.FeePreference{
 			ConfTarget: uint32(in.TargetConf),
@@ -1122,7 +1123,7 @@ func (r *rpcServer) SendMany(ctx context.Context,
 
 	// Based on the passed fee related parameters, we'll determine an
 	// appropriate fee rate for this transaction.
-	satPerKw := lnwallet.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
+	satPerKw := chainfee.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
 	feePerKw, err := sweep.DetermineFeePerKw(
 		r.server.cc.feeEstimator, sweep.FeePreference{
 			ConfTarget: uint32(in.TargetConf),
@@ -1504,7 +1505,7 @@ func (r *rpcServer) OpenChannel(in *lnrpc.OpenChannelRequest,
 
 	// Based on the passed fee related parameters, we'll determine an
 	// appropriate fee rate for the funding transaction.
-	satPerKw := lnwallet.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
+	satPerKw := chainfee.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
 	feeRate, err := sweep.DetermineFeePerKw(
 		r.server.cc.feeEstimator, sweep.FeePreference{
 			ConfTarget: uint32(in.TargetConf),
@@ -1649,7 +1650,7 @@ func (r *rpcServer) OpenChannelSync(ctx context.Context,
 
 	// Based on the passed fee related parameters, we'll determine an
 	// appropriate fee rate for the funding transaction.
-	satPerKw := lnwallet.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
+	satPerKw := chainfee.SatPerKVByte(in.SatPerByte * 1000).FeePerKWeight()
 	feeRate, err := sweep.DetermineFeePerKw(
 		r.server.cc.feeEstimator, sweep.FeePreference{
 			ConfTarget: uint32(in.TargetConf),
@@ -1847,7 +1848,7 @@ func (r *rpcServer) CloseChannel(in *lnrpc.CloseChannelRequest,
 		// Based on the passed fee related parameters, we'll determine
 		// an appropriate fee rate for the cooperative closure
 		// transaction.
-		satPerKw := lnwallet.SatPerKVByte(
+		satPerKw := chainfee.SatPerKVByte(
 			in.SatPerByte * 1000,
 		).FeePerKWeight()
 		feeRate, err := sweep.DetermineFeePerKw(