Pass UpdateFulfillHTLC message owned, rather than by ref

Most of the message handlers in LDK pass messages to the handler by
reference. This is unnecessarily inefficient and there's no real
reason to do so.

Because we just tweaked what `UpdateFulfillHTLC` messages look
like, this is a good opportunity to make progress here, passing at
least one message owned rather than by reference.

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -13521,7 +13521,7 @@ where
 		&self, counterparty_node_id: PublicKey, msg: msgs::UpdateFulfillHTLC,
 	) {
 		let _persistence_guard = PersistenceNotifierGuard::notify_on_drop(self);
-		let res = self.internal_update_fulfill_htlc(&counterparty_node_id, msg);
+		let res = self.internal_update_fulfill_htlc(&counterparty_node_id, &msg);
 		let _ = handle_error!(self, res, counterparty_node_id);
 	}