Issue #19030: final pieces for proper location of various class attributes located in the metaclass.

Okay, hopefully the very last patch for this issue.  :/

I realized when playing with Enum that the metaclass attributes weren't always displayed properly.

New patch properly locates DynamicClassAttributes, virtual class attributes (returned by __getattr__ and friends), and metaclass class attributes (if they are also in the metaclass __dir__ method).

Also had to change one line in pydoc to get this to work.

Added tests in test_inspect and test_pydoc to cover these situations.