[mlir][ArmSME] Add initial dialect with basic lowering of vector.transfer write to zero

This patch adds support for lowering a `vector.transfer_write` of zeroes
and type `vector<[16x16]xi8>` to the SME `zero {za}` instruction [1],
which zeroes the entire accumulator.

This contributes to supporting a path from `linalg.fill` to SME.

[1] https://developer.arm.com/documentation/ddi0602/2022-06/SME-Instructions/ZERO--Zero-a-list-of-64-bit-element-ZA-tiles-

Reviewed By: awarzynski, dcaballe

Differential Revision: https://reviews.llvm.org/D152508