[clang] [llvm] [AArch64] Implement GCS ACLE intrinsics (PR #96903)

[Sam Elliott via cfe-commits]

https://github.com/lenary approved this pull request.

Thanks, LGTM.

As a follow-up, can you check that the instructions generated from this builtin do inhibit the machine outliner? Maybe all GCS-modifying functions have to inhibit the machine outliner, I'm not 100% sure.

https://github.com/llvm/llvm-project/pull/96903