[clang] [llvm] [HLSL] Implement the `reflect` HLSL function (PR #122992)

[Farzon Lotfi via llvm-commits]

https://github.com/farzonl approved this pull request.

LGTM, but I want to see the `[[maybe_unused]]` and the `#include "llvm/Support/raw_ostream.h"` removed before you merge.

https://github.com/llvm/llvm-project/pull/122992