State metrics possible changes (#5168)

* Registering state from overlay.

* fix

* fix2

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <bkchr@users.noreply.github.com>

substrate/primitives/state-machine/src/ext.rs

@@ -587,6 +587,7 @@ mod tests {
 			].into_iter().collect(),
 			committed: Default::default(),
 			collect_extrinsics: true,
+			stats: Default::default(),
 		}
 	}