f32x4->16x8, 64x2->8x16, and 16x8->8x16.
This allows us to pass more spec tests.

Bug: v8:10507
Change-Id: I1810ce2d17f93529b2e69cf5c767cb7b480b4b49
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2429807Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70128}