Fix compact proof decoding unaccessed last child trie. (#9715)

* fix no child proof attached but root included.

* small stress test for proof of child tries.

* rust fmt

substrate/primitives/trie/src/trie_codec.rs

@@ -161,8 +161,9 @@ where
 	}
 
 	let mut previous_extracted_child_trie = None;
+	let mut nodes_iter = nodes_iter.peekable();
 	for child_root in child_tries.into_iter() {
-		if previous_extracted_child_trie.is_none() {
+		if previous_extracted_child_trie.is_none() && nodes_iter.peek().is_some() {
 			let (top_root, _) =
 				trie_db::decode_compact_from_iter::<L, _, _, _>(db, &mut nodes_iter)?;
 			previous_extracted_child_trie = Some(top_root);