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

[Timm Baeder via cfe-commits]

tbaederr wrote:

Sure but clang 16 will emit a warning for them: https://godbolt.org/z/jnsc4336G - are we passing `-Wno-unknown-attributes` to the build?

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