These were not added in https://crrev.com/c/2026067 when we added
similar tests for other lane sizes, since x64 had a completely different
path for i8x16. But this tests are useful anyway for other archs, so add
them in.

Bug: v8:10115
Change-Id: I77ecca0cd9f4021c94f1538aa5635b5d54983207
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2041708Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66178}