This adds the missing implementation of bulk memory operations on 64-bit
memory on 32-bit systems. This is tricky because especially on ia32 we
don't have a lot of registers, so we cannot keep three 64-bit values
in registers at the same time.
Thus combine the high words into a single register early, and use a
single zero-check afterwards.

R=thibaudm@chromium.org

Bug: v8:10949, chromium:1281995
Change-Id: I017bc43989e4b6195b46b5d0738552a685362e43
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3468335Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/main@{#79196}