The old code was relying on identical alignment of both the source and
the destination of the Relaxed_Memcpy. This is not always given, thus
check for alignment of both.

R=mlippautz@chromium.org

Bug: chromium:1208782, v8:11704
Change-Id: Ic5dca3a5f0ecaea0df6eb123105520bd7785853c
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2905611Reviewed-by: Michael Lippautz <mlippautz@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#74694}