[clang] [HLSL] Finish exposing half types and intrinsics always (PR #132804)

[Chris B via cfe-commits]

https://github.com/llvm-beanz commented:

this is not NFC, so we should verify that we can call these intrinsics with `half` values even if 16-bit types aren't enabled, and that they properly codegen to 32-bit variants.

https://github.com/llvm/llvm-project/pull/132804