This is a reland of 94f2212b

Nothing changed, think the failures were flaky.

Original change's description:
> [wasm-simd] Scalar lowering for extended multiply
>
> R=bbudge@chromium.org
>
> Bug: v8:11262
> Change-Id: Idd6a7514a16c561832af603dbf63779a0e402f45
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2603771
> Reviewed-by: Bill Budge <bbudge@chromium.org>
> Commit-Queue: Zhi An Ng <zhin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71920}

Bug: v8:11262
Change-Id: I6c504b2e0d1ad39e202483a72419dadb3b66eea8
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2612330Reviewed-by: Bill Budge <bbudge@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71965}