[AArch64][SVE] CodeGen of ACLE Builtin Types

Summary:
This patch adds codegen support for the ACLE builtin types added in:

  https://reviews.llvm.org/D62960

so that the ACLE builtin types are emitted as corresponding scalable
vector types in LLVM.

Reviewers: rsandifo-arm, rovka, rjmccall, efriedma

Reviewed By: efriedma

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

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D74724