[llvm] [mlir] [mlir][gpu] Change GPU modules to globals (PR #135478)

[Mehdi Amini via llvm-commits]

joker-eph wrote:

`git grep CUDA_MODULE_LOADING` does not find anything in the repo, do you have a pointer to what you have in mind here?

https://github.com/llvm/llvm-project/pull/135478