Restore compatibility with older cuda-bindings

[leofang]

@brandon-b-miller get_cuda_native_handle was not added until very recently (12.9.1), so this will break users who are using older cuda-bindings 12.x. I suggest this:

try:
    from cuda.bindings.utils import get_cuda_native_handle
except ImportError:
    def get_cuda_native_handle(obj):
       return int(obj)

Originally posted by @leofang in #401 (comment)

[brandon-b-miller]

Don't we require >=12.9.1 for both pip and conda packages now?

[leofang]

Yes, you're absolutely right Brandon, I had forgotten about #387... Sorry!