[hwasan] Add intrinsics for fixed shadow on Aarch64 (#89319)

This patch introduces HWASan memaccess intrinsics that assume a fixed
shadow (with the offset provided by --hwasan-mapping-offset=...), with
and without short granule support.

The behavior of HWASan is not meaningfully changed by this patch;
future work ("Optimize outlined memaccess for
fixed shadow on Aarch64": https://github.com/llvm/llvm-project/pull/88544) will make HWASan use these intrinsics.

We currently only support lowering the LLVM IR intrinsic to AArch64.

The test case is adapted from hwasan-check-memaccess.ll.