[clang] [llvm] [HLSL][SPIR-V] Implements SV_Position for VS/PS I/O (PR #168735)

[Nathan Gauër via llvm-commits]

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Keenuts wrote:

Added 6 news tests in the correct location: clang/test/AST/HLSL, keeping this as removed since AST tests are not supposed to be in sema.

https://github.com/llvm/llvm-project/pull/168735