The flutterroot param is accessible from the util function after the recent refactor of utils https://github.com/flutter/flutter/pull/146592 so this change cleans up the references to the suite runners to make them simpler. Part of https://github.com/flutter/flutter/issues/145482
Refactor docs testing suite in order to reduce testing logic in test.dart and allow for later implementing package:test onto the existing docs tests Part of https://github.com/flutter/flutter/issues/145482