Rename NUMBAPRO cuda related environment variables + refactor.

As noted in https://github.com/numba/numba/issues/2849, there are a number of NUMBAPRO prefixed environment variables still in use that could do with a name change:

NUMBAPRO_VERBOSE_CU_JIT_LOG
NUMBAPRO_CUDA_LOG_SIZE
NUMBAPRO_CUDA_DRIVER
NUMBAPRO_LIBDEVICE
NUMBAPRO_CUDALIB
NUMBAPRO_NVVM

and as suggested a NUMBA_CUDA_SDK env var that lets you specify the top-level CUDA directory and infers the rest of the paths needed would be good.

[stuartarchibald]

@AndiH

• Anything with NUMBAPRO is from a really long while back and needs looking at for deprecation/updating.
• CUDA toolkit/runtime etc has changed a bit through time so some things that used to be useful/present now aren’t and the code probably exhibits these artifacts (as noted!).

Agree that NUMBA_CUDA_SDK is the thing to set, and CUDA_PATH/CUDA_ROOT could also be queried as a place to look if the env var and the default locations are fruitless, good idea.

To do the work for this, anything NUMBAPRO + CUDA related would need deprecation marks/warnings applied, then the new behaviour implemented and documented, along with a plan for final removal of the old.

[seibert]

Closing this issue as 0.44 contains a reworked CUDA environment detection heuristic. (See #4096 for more details.)