Require only CUDA wheels (no system CTK) in pip packages

[bdice]

Installing RAPIDS via pip should work with only CUDA wheels, with no requirement for a system CUDA Toolkit (only a driver).

Benefits:

• This would allow us to shrink our citestwheel CI image significantly.
• Users would use a single, consistent CTK source for all libraries adjacent to RAPIDS

Work tracked in #35, #137 added support for using CUDA wheels for math libraries. I think we already statically link the runtime in all our wheel builds, which is discussed in #4.

The action items I know of are primarily in RAPIDS dependencies, including cupy and numba-cuda:

• Allow using CUDA libraries installed from pip wheels cupy/cupy#8013
• [FEA] Support for loading NVRTC from a wheel NVIDIA/numba-cuda#66
• [FEA] Support for loading NVVM from a wheel NVIDIA/numba-cuda#65

This issue should be used to track those items and any other dependencies.