Python 3.13 removed the old buffer interface

[totaam]

for details, see python/cpython#85275

I'm not sure what CUDAPP_CALL_GUARDED does or if we perhaps should catch errors there and call PyBuffer_Release if an error is thrown.
I also don't know if the failures here are meant to be fatal or not.

Only compile tested at this point.

[inducer]

Thanks for putting this together. I share your concern about exception safety, at least in the C++ code. Fortunately, there already is a RAII wrapper for the buffer interface floating around, I've simply changed the code there to use that.