Merge #3767

3767: [Network] Fix inbound message metrics label r=peterargue a=peterargue

`PayloadType()` is used when generating incoming metrics labels. `m.msg.Payload` is always a byte slice, whereas `m.decodedPayload` is the actual message struct

Co-authored-by: Peter Argue <89119817+peterargue@users.noreply.github.com>

network/message_scope.go

@@ -100,7 +100,7 @@ func (m IncomingMessageScope) EventID() []byte {
 }
 
 func (m IncomingMessageScope) PayloadType() string {
-	return MessageType(m.msg.Payload)
+	return MessageType(m.decodedPayload)
 }
 
 // OutgoingMessageScope captures the context around an outgoing message that is about to be sent.