[clang] [clang][NFC] Annotate `Type` bit-fields with `clang::preferred_type` (PR #70349)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> We definitely need to wrap these in a macro/hide them in a macro somehow. This will fail `-Werror` on GCC/MSVC/Older Clang compilers.

+1, the macro would live in https://github.com/llvm/llvm-project/blob/main/llvm/include/llvm/Support/Compiler.h along with the other attribute macros.

https://github.com/llvm/llvm-project/pull/70349