This implements v128.const for ia32, x64, arm, and arm64.

Moves one of the test case under the correct header.

Bug: v8:9909
Change-Id: I93eb179ac5fd0bc22e3dd5277f7d73699ac8b452
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2290623
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68806}