lnwallet: delegate all channel funding logic to the new chanfunding package

In this commit, we begin to integrate the new channel funding package
into the existing codebase. With this set of changes, we'll no longer
construct and sign the funding transaction within this package, instead
delegating it to the new chanfunding package. We use the new
chanfunding.WalletAssembler to carry out all channel funding, providing
it with an implementation of all its interfaces backed by the wallet.

lnwallet/reservation.go

@@ -11,6 +11,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
+	"github.com/lightningnetwork/lnd/lnwallet/chanfunding"
 	"github.com/lightningnetwork/lnd/lnwire"
 )
 
@@ -114,7 +115,10 @@ type ChannelReservation struct {
 	// commitment state.
 	pushMSat lnwire.MilliSatoshi
 
-	wallet *LightningWallet
+	wallet     *LightningWallet
+	chanFunder chanfunding.Assembler
+
+	fundingIntent chanfunding.Intent
 }
 
 // NewChannelReservation creates a new channel reservation. This function is
@@ -124,8 +128,8 @@ type ChannelReservation struct {
 func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 	commitFeePerKw chainfee.SatPerKWeight, wallet *LightningWallet,
 	id uint64, pushMSat lnwire.MilliSatoshi, chainHash *chainhash.Hash,
-	flags lnwire.FundingFlag,
-	tweaklessCommit bool) (*ChannelReservation, error) {
+	flags lnwire.FundingFlag, tweaklessCommit bool,
+	fundingAssembler chanfunding.Assembler) (*ChannelReservation, error) {
 
 	var (
 		ourBalance   lnwire.MilliSatoshi
@@ -213,6 +217,14 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 		} else {
 			chanType |= channeldb.SingleFunderBit
 		}
+
+		// If this intent isn't one that's able to provide us with a
+		// funding transaction, then we'll set the chanType bit to
+		// signal that we don't have access to one.
+		if _, ok := fundingAssembler.(chanfunding.FundingTxAssembler); !ok {
+			chanType |= channeldb.NoFundingTxBit
+		}
+
 	} else {
 		// Otherwise, this is a dual funder channel, and no side is
 		// technically the "initiator"
@@ -253,6 +265,7 @@ func NewChannelReservation(capacity, localFundingAmt btcutil.Amount,
 		pushMSat:      pushMSat,
 		reservationID: id,
 		wallet:        wallet,
+		chanFunder:    fundingAssembler,
 	}, nil
 }