Refactor and test spec block rules (#4670)

* Refactor and test spec block rules

* address review

* Update client/src/block_rules.rs

Co-Authored-By: André Silva <andre.beat@gmail.com>

Co-authored-by: André Silva <andre.beat@gmail.com>

substrate/client/block-builder/src/lib.rs

@@ -197,8 +197,6 @@ where
 		)?;
 		let parent_hash = self.parent_hash;
 
-		// The unsafe is required because the consume requires that we drop/consume the inner api
-		// (what we do here).
 		let storage_changes = self.api.into_storage_changes(
 			&state,
 			changes_trie_state.as_ref(),