record: stricter type for PaymentRelayInfo.BaseFee

In this commit, we update the PaymentRelayInfo struct's BaseFee member
to use a stricter type (lnwire.MilliSatoshi) instead of an ambigious
uint32.

record/blinded_data_test.go

@@ -37,7 +37,7 @@ func TestBlindedDataEncoding(t *testing.T) {
 
 	tests := []struct {
 		name        string
-		baseFee     uint32
+		baseFee     lnwire.MilliSatoshi
 		htlcMin     lnwire.MilliSatoshi
 		features    *lnwire.FeatureVector
 		constraints bool