Only run aggressive test_node_counter_consistency in tests

`test_node_counter_consistency` can make gossip operations *really*
slow. This makes it a pretty bad idea in a general node just
running in debug mode. It also makes our
`lightning-rapid-gossip-sync` real-world test painfully slow.

Thus, here, we make `test_node_counter_consistency` only actually
run in the `lightning`-crate tests, rather than always with
`debug_assertions`.

Author: TheBlueMatt

lightning/src/routing/gossip.rs

@@ -1786,7 +1786,7 @@ where
 	}
 
 	fn test_node_counter_consistency(&self) {
-		#[cfg(debug_assertions)]
+		#[cfg(test)]
 		{
 			let channels = self.channels.read().unwrap();
 			let nodes = self.nodes.read().unwrap();