[clang] [llvm] [HLSL][SPIR-V] Implement vk::ext_builtin_input attribute (PR #138530)

[Nathan Gauër via llvm-commits]

Keenuts wrote:

Rebased, tests not pass (HLSL, and locally for the rest). The CI is quite busy today so the rest is still pending.
Adding more reviewers for the final round
@llvm-beanz for the Microsoft side
@arsenm for the AMDGPU address space bit



https://github.com/llvm/llvm-project/pull/138530