bindings: python: provide better resource control

bindings: python: provide better resource control

So far we rely on cpython's reference counting for closing the GPIO
chips and freeing the underlying resources. This is however wrong.
Python doesn't guarantee anything regarding the lifetime of an object.

Provide a method for closing the underlying chip handle and add
relevant checks to all methods using the resources associated with
a GPIO chip, so that we raise an error should the user use a chip
after closing it.

Signed-off-by: Bartosz Golaszewski <bartekgola@gmail.com>