lnwire: add new TestMessage interface for property tests

In this commit, we add a new `TestMessage` interface for use in property
tests. With this, we'll be able to generate a random instance of a given
message, using the rapid byte stream. This can also eventually be useful
for fuzzing.

lnwire/reply_channel_range.go

@@ -70,7 +70,8 @@ func NewReplyChannelRange() *ReplyChannelRange {
 // lnwire.Message interface.
 var _ Message = (*ReplyChannelRange)(nil)
 
-// A compile time check to ensure ReplyChannelRange implements the lnwire.SizeableMessage interface.
+// A compile time check to ensure ReplyChannelRange implements the
+// lnwire.SizeableMessage interface.
 var _ SizeableMessage = (*ReplyChannelRange)(nil)
 
 // Decode deserializes a serialized ReplyChannelRange message stored in the