This is required to be spec-compliant.
The previously implemented behavior was more relaxed allowing one to use
`ref.cast null` on non-nullable inputs and still getting a non-nullable
result on cast success.
Bug: v8:7748
Change-Id: I1297314389b0445a7c8d5a74f37d07a723d7a133
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/4091549
Reviewed-by: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Matthias Liedtke <mliedtke@chromium.org>
Cr-Commit-Position: refs/heads/main@{#84776}