bpo-43682: @staticmethod inherits attributes (GH-25268)

Static methods (@staticmethod) and class methods (@classmethod) now
inherit the method attributes (__module__, __name__, __qualname__,
__doc__, __annotations__) and have a new __wrapped__ attribute.

Changes:

* Add a repr() method to staticmethod and classmethod types.
* Add tests on the @classmethod decorator.
8 files changed