Use ClassLoaderData::classes_do for CDS classes

ClassDataSharing classes should be dumped using the ClassLoaderData::_classes list. Currently the code uses SystemDictionary::dictionary() which also contains classes that are initiated by different loaders than owning loaders. Practically this doesn't affect CDS, since only the boot loader is present, but it necessitates calling the SystemDictionary::classes_do() function that passed the ClassLoaderData because some loaders in the table are NULL for CDS.

The list of loaded classes is found on the ClassLoaderData and includes array classes, anonymous classes, redefined classes, and unloaded classes. For CDS the closure filters these out.