The interpreter is missing a static cast when extracting lanes smaller
than int32_t and doing an unsigned extend. The array in Simd128 is
signed, so a direct cast to uint32_t will be a signed extension. The fix
is to, in the unsigned case, cast to unsigned (of the appropriate size)
first, then cast to uint32_t.

Change-Id: Ifabb5b9690f08ad505ac94b84908db0970581818
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2216721Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68029}