Fix benchmark read/write key tracker for keys in child storages. (#6905)

* WIP: read child trie and write child trie

* add test

* refactor a bit + improve log

* better naming

* trigger CI

* Revert "trigger CI"

This reverts commit d0aadaeb6a12fc6c39f01b3c1b5725d19f085865.

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

@@ -594,6 +594,7 @@ where
 			changes.transaction_storage_root,
 			changes.transaction,
 			changes.main_storage_changes,
+			changes.child_storage_changes,
 		).expect(EXT_NOT_ALLOWED_TO_FAIL);
 		self.mark_dirty();
 		self.overlay