[clang] [clang-tools-extra] [PAC][clang] Define `PointerAuthQualifier` and `PointerAuthenticationMode` (PR #84384)

[Daniil Kovalev via cfe-commits]

kovdan01 wrote:

@AaronBallman @rjmccall Please see 53485b1e7f7c60253b8734e95ae9b9a04e9e7a95 commit which makes `Mask` 64-bit and removes separate `PtrAuth` field in `Qualifiers`. The performance becomes better:

- before https://llvm-compile-time-tracker.com/compare.php?from=3ae10fde39419d7c985b9fff210ed44b699e438c&to=ed334d7dba24c53d39c8994d51440e34f6d3b375

- after https://llvm-compile-time-tracker.com/compare.php?from=3ae10fde39419d7c985b9fff210ed44b699e438c&to=7c4ee3fd79a0cda33e60b4681ec327055d5f5c20

https://github.com/llvm/llvm-project/pull/84384