[clang] [clang][ptrauth] Add support for querying the ptrauth schema of a type (PR #138482)

[Oliver Hunt via cfe-commits]

ojhunt wrote:

Adding @cor3ntin and @AaronBallman in case they have a better idea for getting the function key to Sema than having it duplicated in langopts and codegen options

https://github.com/llvm/llvm-project/pull/138482