[llvm] [C API] Support new ptrauth constant type (PR #93909)

[Benji Smith via llvm-commits]

Benjins wrote:

Merged from main and added some annotations to skip clang formatting on the macro it had trouble with

> Given the stability guarantees of C API, I would wait until we will have end-to-end implementation from frontend to backend just in case.

@asl From the commit history, it seems like `ptrauth` constants are now used in Clang and the AArch64 backend. It seems like the fields for `ConstantPtrAuth` are the same as before. Does this PR seem good to land now?

https://github.com/llvm/llvm-project/blob/5b310a1c3c5aabae325934a6475e93ea8b71cdc2/llvm/include/llvm/IR/Constants.h#L1026-L1027

https://github.com/llvm/llvm-project/pull/93909