[clang] [HLSL][SPIR-V] Add hlsl_private address space for HLSL/SPIR-V (PR #122103)

[Nathan Gauër via cfe-commits]

Keenuts wrote:

> Is there a reason we can't do this in Sema? It would probably be ideal to have the AST represent the address spaces of values accurately.

Hello! So I didn't recalled the details on why, so I made another PR which implements this in sema (https://github.com/llvm/llvm-project/pull/133464)

https://github.com/llvm/llvm-project/pull/122103