Prototype these 4 instructions:

- i64x2.widen_low_i32x4_s
- i64x2.widen_high_i32x4_s
- i64x2.widen_low_i32x4_u
- i64x2.widen_high_i32x4_u

Bug: v8:10972
Change-Id: I3defd0a2431252bc3f5bb45e022e62b37beb34ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2601012
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71888}