Implement i32x4.dot_i16x8_s for Liftoff on on ia32 and x64.
ARM implementation will come later.

Bug: v8:10993
Change-Id: I33b859a21b91023b40d8cf7b9fee110b0d148a7c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2477497Reviewed-by: Clemens Backes <clemensb@chromium.org>
Commit-Queue: Zhi An Ng <zhin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#70583}