lnwallet: simplify fee calculation in evaluateHTLCView

This commit simplifies how we compute the commitment fee rate based
off of the live updates. Prior to this commit we processed all of
the FeeUpdate paymentDescriptors of both ChannelParty's. Now we only
process the last FeeUpdate of the OpeningParty

lnwallet/channel_test.go

@@ -8650,6 +8650,7 @@ func TestEvaluateView(t *testing.T) {
 		name             string
 		ourHtlcs         []*paymentDescriptor
 		theirHtlcs       []*paymentDescriptor
+		channelInitiator lntypes.ChannelParty
 		whoseCommitChain lntypes.ChannelParty
 		mutateState      bool
 
@@ -8679,6 +8680,7 @@ func TestEvaluateView(t *testing.T) {
 	}{
 		{
 			name:             "our fee update is applied",
+			channelInitiator: lntypes.Local,
 			whoseCommitChain: lntypes.Local,
 			mutateState:      false,
 			ourHtlcs: []*paymentDescriptor{
@@ -8696,6 +8698,7 @@ func TestEvaluateView(t *testing.T) {
 		},
 		{
 			name:             "their fee update is applied",
+			channelInitiator: lntypes.Remote,
 			whoseCommitChain: lntypes.Local,
 			mutateState:      false,
 			ourHtlcs:         []*paymentDescriptor{},
@@ -8911,8 +8914,10 @@ func TestEvaluateView(t *testing.T) {
 		test := test
 
 		t.Run(test.name, func(t *testing.T) {
+			isInitiator := test.channelInitiator == lntypes.Local
 			lc := LightningChannel{
 				channelState: &channeldb.OpenChannel{
+					IsInitiator:       isInitiator,
 					TotalMSatSent:     0,
 					TotalMSatReceived: 0,
 				},