This specific case was not implemented or tested before. Implementing it
actually simplifies some of the existing logic, since StepOut can now
reuse the generic logic in debug.cc for all cases (Wasm->Wasm, Wasm->JS,
JS->Wasm).

Drive-by:
1) Fix typo ("skip" -> "step").
2) Move the check for Liftoff code from debug.cc to wasm-debug.cc, where
   it fits better.
3) Remove a TODO which is done already.

R=thibaudm@chromium.org, szuend@chromium.org

Bug: chromium:1145176
Change-Id: I415ca1d8bacef5b21bf1dafd9e16417ec2d12c7c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2560719
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Simon Zünd <szuend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#71428}