multi: refactor lnwallet/channel.go to use ChannelParty in select places

We also include changes to contractcourt, htlcswitch and peer to stitch the
boundaries together.

lnwallet/wallet.go

@@ -25,6 +25,7 @@ import (
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/keychain"
+	"github.com/lightningnetwork/lnd/lntypes"
 	"github.com/lightningnetwork/lnd/lnwallet/chainfee"
 	"github.com/lightningnetwork/lnd/lnwallet/chanfunding"
 	"github.com/lightningnetwork/lnd/lnwallet/chanvalidate"
@@ -1475,10 +1476,12 @@ func CreateCommitmentTxns(localBalance, remoteBalance btcutil.Amount,
 	leaseExpiry uint32) (*wire.MsgTx, *wire.MsgTx, error) {
 
 	localCommitmentKeys := DeriveCommitmentKeys(
-		localCommitPoint, true, chanType, ourChanCfg, theirChanCfg,
+		localCommitPoint, lntypes.Local, chanType, ourChanCfg,
+		theirChanCfg,
 	)
 	remoteCommitmentKeys := DeriveCommitmentKeys(
-		remoteCommitPoint, false, chanType, ourChanCfg, theirChanCfg,
+		remoteCommitPoint, lntypes.Remote, chanType, ourChanCfg,
+		theirChanCfg,
 	)
 
 	ourCommitTx, err := CreateCommitTx(