[AArch64][SVE2] Implement while comparison intrinsics

Summary:
Adds the following intrinsics:

    * whilege, whilegt, whilehi, whilehs

Reviewers: sdesmalen, rovka, dancgr, efriedma, rengolin, huntergr

Reviewed By: sdesmalen

Subscribers: tschuett, kristof.beyls, hiraditya, rkruppe, psnobl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70909