[AArch64][SVE] SVE2 intrinsics for character match & histogram generation

Summary:
Implements the following intrinsics:
 - @llvm.aarch64.sve.histcnt
 - @llvm.aarch64.sve.histseg
 - @llvm.aarch64.sve.match
 - @llvm.aarch64.sve.nmatch

Reviewers: c-rhodes, sdesmalen, dancgr, efriedma, rengolin

Reviewed By: c-rhodes

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74117