[clang] [llvm] [HLSL][SPIR-V] Implement vk::location for inputs (PR #169479)

[Nathan Gauër via cfe-commits]

Keenuts wrote:

@s-perron @tex3d this PR is ready for review, but is based on #168743. Please review by only looking at the last commit of the stack related to locations.

https://github.com/llvm/llvm-project/pull/169479