[wasm][liftoff] Always zero-extend 32 bit offsets

The upper 32 bits of the 64 bit offset register are not guaranteed to be
cleared, so a zero-extension is needed. We already do the zero-extension
in the case of explicit bounds checking, but this should also be done if
the trap handler is enabled.

R=clemensb@chromium.org
CC=jkummerow@chromium.org

Bug: v8:11809
Change-Id: I21e2535c701041d11fa06c176fa683d82db0a3f1
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2917612


Commit-Queue: Thibaud Michaud <thibaudm@chromium.org>
Reviewed-by: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74881}