Load and zero extend is still in prototype phase [0], implementing for ARM64 in
order to get more benchmark results.

[0] https://github.com/WebAssembly/simd/pull/237

Bug: v8:10713
Change-Id: I7d632324e4bdb0934ab024911201a06b19a1a83d
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2416407
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70069}