- Remove fixed TODOs
- Fix typo
- Add a couple of types in subtyping tests

Bug: v8:7748
Change-Id: I757fa60ffe4fe9f9361cf0c4e9ca88b31747459f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2282529
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68700}