[llvm] [NVPTX] Add tex.grad.cube{array} intrinsics (PR #77693)

[Artem Belevich via llvm-commits]

Artem-B wrote:

> @Artem-B, the changes to `llvm/test/CodeGen/NVPTX/surf-tex.py` add coverage for these intrinsics, is there additional testing you'd like?

Ah. It was not obvious. Can you please verify that the test does contain the new instructions and that LLVM tests pass with `LLVM_PTXAS_EXECUTABLE=/path/to/ptxas` set in the environment.

https://github.com/llvm/llvm-project/pull/77693