After calling the ToNumber builtin, we are guaranteed to get either a
Smi or a HeapNumber. Thus we can skip the check for undefined, which
removes quite some unneeded code from wasm-to-js and js-to-wasm
wrappers.

R=ahaas@chromium.org

Bug: v8:10070
Change-Id: I0e2ad19f1575fb6979222e324fbdb71aaf85e6fd
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1962279
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65520}