This patch does not include support for RTTs for i31ref yet.

Bug: v8:7748
Change-Id: Ifbeb8e305c2d0a57e4d5d6be761d046e330e0da1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2273135
Commit-Queue: Michael Achenbach <machenbach@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68613}