[AArch64][SVE] Add missing debug info for ACLE types.

This patch adds type information for SVE ACLE vector types,
by describing them as vectors, with a lower bound of 0, and
an upper bound described by a DWARF expression using the
AArch64 Vector Granule register (VG), which contains the
runtime multiple of 64bit granules in an SVE vector.

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D86101