[AArch64][SVE] Asm: Add support for parsing and printing SVE vector lists.

Summary:
Added Z_(b|h|s|d) vector list RegisterOperands along with support to
add/print the vector lists.

This is patch [5/6] in a series to add assembler/disassembler support for
SVE's contiguous ST1 (scalar+imm) instructions.

Reviewers: fhahn, rengolin, javed.absar, huntergr, SjoerdMeijer, t.p.northover, echristo, evandro

Reviewed By: fhahn

Subscribers: tschuett, kristof.beyls, llvm-commits

Differential Revision: https://reviews.llvm.org/D45431

llvm-svn: 330000