[clang] [CIR][CUDA] Handle local, __device__, __shared__, and __constant__ variables (PR #184248)

[Zaky Hermawan via cfe-commits]

ZakyHermawan wrote:

I am adding __constant__ support, since I think it is related, also Mark device variables as externally_initialized.
One note: I remove CIR-HOST, LLVM-HOST, and OGCG-HOST from test in global-vars.cu, because shadow variable did not properly implemented, yet.

https://github.com/llvm/llvm-project/pull/184248