This is essentially a revert of 3 commits:

- a1d39bba
- 5a0938e5
- 74362ae3

with merge conflicts fixed.

These instructions were not merged into the SIMD proposal.

Bug: v8:11297
Change-Id: Ifffe7c61cae10fadc345d0faa1b0ba45ce74e946
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2704950Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72933}