[AArch64][SVE] Implement additional integer arithmetic intrinsics

Summary:
Add intrinsics for the following:
  - sxt[b|h|w] & uxt[b|h|w]
  - cls & clz
  - not & cnot

Reviewers: huntergr, sdesmalen, dancgr

Reviewed By: sdesmalen

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D69567