gh-80384: Check that callback is callable at weak reference creation (GH-151145)

gh-80384: Check that callback is callable at weak reference creation (GH-151145)

* Python functions weakref.ref() and weakref.proxy() now raise TypeError
  if the callback argument is not callable or None.
* C functions PyWeakref_NewRef() and PyWeakref_NewProxy() now raise TypeError
  if the callback argument is not callable, None, or NULL.

Co-authored-by: Maxwell Bernstein <emacs@fb.com>