Changes:
- Remove the restriction that ref.test, ref.cast and br_on_cast may only
  cast to subtypes of the cast object's type. Optimize unrelated type
  casts in the decoder. Add tests.
- Generalize Unreachable() interface function to Trap(TrapReason).
- Fix rtt.sub to be able to accept an rtt without depth. Modify related
  test accordingly.
- Type local.tee according to the local's type as opposed to the value's
  type.

Bug: v8:7748, v8:11541
Change-Id: I4d1846a2cfda891d32a9c1ed26781e4518d4cdf9
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2756210Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Manos Koukoutos <manoskouk@chromium.org>
Cr-Commit-Position: refs/heads/master@{#73461}