[AArch64][SVE] Add SVE2 intrinsics for uniform DSP operations

Summary:
Implements the following intrinsics:
 - sqrdmlah, sqrdmlsh, sqrdmulh & sqdmulh
 - [s|u]hadd, [s|u]hsub, [s|u]rhadd & [s|u]hsubr
 - urecpe, ursqrte, sqabs & sqneg

Reviewers: sdesmalen, efriedma, dancgr, cameron.mcinally

Reviewed By: efriedma

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

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73493