Changes:
- Remove subtyping checks from value-type.h and move them to dedicated
  files. Leave a limited version in value-type.h for testing.
- Implement subtyping for struct and array types, according to the
  wasm-gc proposal.
- Implement type equivalence checking.
- Introduce a subtyping relation cache in WasmModule.
- Rename IsSubTypeOf -> IsSubtypeOf.
- Fix v8 possible bug where iterator_range took two unused type
  parameters.
- Add unittests for subtyping.

Bug: v8:7748
Change-Id: I0ddbda4145e0412196dcf4fc63f3c5875fb3ab5a
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2228497
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68192}