- Adapt subtyping unittest to the new HeapType API
- Generalize WASM_REF_TYPE macro

Bug: v8:7748
Change-Id: Ifdb24408d7a34a6470ddccdf3dc8536cbb93dece
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2274610
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68652}