[AArch64][GlobalISel] Implement __builtin_return_address for PAC-RET

This patch implements stripping of the PAC in the return address for GlobalISel.

Implementation for when not using GLobalISel is in
https://reviews.llvm.org/D75044 The analogous GCC patch is
https://gcc.gnu.org/git/?p=gcc.git;a=commitdiff;h=a70d5d81c41048556fd86eaa1036018a6bfba115

Differential Revision: https://reviews.llvm.org/D84502