[llvm] [NVPTX] Vectorize and lower 256-bit global loads/stores for sm_100+/ptx88+ (PR #139292)

[Drew Kersnar via llvm-commits]

dakersnar wrote:

I think I addressed all current feedback, although the removal of the VecType operand is causing some tests to fail, I'll need to investigate what I'm missing on Monday but saving my progress for now.

Also, @AlexMaclean do you know if NVPTXForwardParams.cpp need to be updated to include the v8 opcodes?

https://github.com/llvm/llvm-project/pull/139292