[clang] [llvm] [HLSL] Implement '__builtin_hlsl_is_intangible' type trait (PR #104544)

[Chris B via cfe-commits]

https://github.com/llvm-beanz approved this pull request.

Overall looks good. I think that in the places outside SemaHLSL we should try to refer to the trait as `HLSLIntangible` to make it clear that it is a language-mode specific feature. We don't need to repeat HLSL a million times in SemaHLSL because that would just be noisy and redundant.

https://github.com/llvm/llvm-project/pull/104544