peer: stop extracting InboundFees

Like the previous commit, here we can start directly using the
InboundFee on the models.ChannelEdgePolicy object since we know we read
it from disk and so the InboundFee field will be populated accordingly.

NOTE: unlike the previous commit, behaviour is slightly different here
since previously we would error out here if TLV parsing failed whereas
now, the DB call will just skip the error and return a nil policy. This
should be ok since this is explicitly only dealing with our own updates
and so our TLV should always be valid.

peer/brontide.go

@@ -1205,27 +1205,17 @@ func (p *Brontide) loadActiveChannels(chans []*channeldb.OpenChannel) (
 		// routing policy into a forwarding policy.
 		var forwardingPolicy *models.ForwardingPolicy
 		if selfPolicy != nil {
-			var inboundWireFee lnwire.Fee
-			_, err := selfPolicy.ExtraOpaqueData.ExtractRecords(
-				&inboundWireFee,
-			)
-			if err != nil {
-				return nil, err
-			}
-
-			inboundFee := models.NewInboundFeeFromWire(
-				inboundWireFee,
-			)
-
 			forwardingPolicy = &models.ForwardingPolicy{
 				MinHTLCOut:    selfPolicy.MinHTLC,
 				MaxHTLC:       selfPolicy.MaxHTLC,
 				BaseFee:       selfPolicy.FeeBaseMSat,
 				FeeRate:       selfPolicy.FeeProportionalMillionths,
 				TimeLockDelta: uint32(selfPolicy.TimeLockDelta),
-
-				InboundFee: inboundFee,
 			}
+			selfPolicy.InboundFee.WhenSome(func(fee lnwire.Fee) {
+				inboundFee := models.NewInboundFeeFromWire(fee)
+				forwardingPolicy.InboundFee = inboundFee
+			})
 		} else {
 			p.log.Warnf("Unable to find our forwarding policy "+
 				"for channel %v, using default values",