This is a reland of dc369749
Changes: relaxed --liftoff-only mode to still allow bailing
out due to missing CPU support.

Original change's description:
> [wasm-gc] Liftoff support part 4: subtyping
>
> This adds support for the following instructions:
> struct.new_default, rtt.sub, ref.test, ref.cast
>
> Bug: v8:7748
> Change-Id: I7423ddd7a83c80cb1e82c620780c27bec59ec762
> Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2593341
> Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
> Reviewed-by: Clemens Backes <clemensb@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#71805}

Bug: v8:7748
Change-Id: If31fcee5e7e173d7c2a6e1c624f4ff04cec7fe9c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2596338
Auto-Submit: Jakob Kummerow <jkummerow@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71823}