Focus: Changed event to setfocus.wb and added test and helper for same page link focus changes

Had to change to setfocus.wb because triggering focus.wb was also triggering the native focus event which interfered with focus change fixes for screen readers and Chrome/Safari.

This approach only tests once and deregisters if not needed.

TODO: Handling of deep linking from a different page (since Chrome/Safari have same bug for deep links as for same page links... to be handled in separate PR)