[llvm] [AArch64][PAC] Refine authenticated pointer check methods (PR #74074)

[David Spickett via llvm-commits]

DavidSpickett wrote:

Yes, that's what I meant.

Even if it's "consistent numbers were chosen for consistency's sake only", it's good to record that.

https://github.com/llvm/llvm-project/pull/74074