This adds support for the following instructions:
br_on_null, ref.as_non_null, br_on_cast, i31.new

Bug: v8:7748
Change-Id: I210b8979327ea0031f89748b71b51abbac10bb8b
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2590041
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71773}