Support new cuda-python layout

[vyasr]

cuda-python 12.6.1 (11.8.4 on the CUDA 11 line) introduces a new layout and deprecates the old one. This is not considered a breaking change for them, but it is for much of RAPIDS CI where warnings are treated as errors. In the short term, the resolution is #116, which adds pinnings to avoid this problem (as well as others). Longer-term, we probably do not want to just change our imports because that would make us require only the latest versions of the package, which would be fairly constraining and could make our environments unsolveable if other libraries do not make similar updates. Instead, we will need to handle this importing conditionally to ensure that we can get what we need. Presumably this doesn't impact cimports since those would be Cython build warnings (and we are generally not blocked on those), so conditional imports should be sufficient to enable a broader range of usability.