Loop fallthroughs should leave values according to their out-type on the
stack, even when the stack is polymorphic.

Bug: chromium:1217470
Change-Id: I0a7e0569fa24fc16fcac76569a5ba14b6c7b0a9f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2949090Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75043}