Get map of WSDL-defined attribute QNames for this component, indexed by
canonical QName string (see
javax.xml.namespace.QName.toString .
Implementation note: since this method is declared in the public API
interface, it has to be a member, not static. We delegate
to a class method to do the actual work.
Map of WSDL-defined attribute QNames for this component, indexed by QName.toString()