This CL adds handling for Load/StoreMessage to LoadElimination. It is
handled like a Load/StoreField to an external location.

Change-Id: I50f27fba9cb7ffabf1474aa409083676cef65442
Bug: v8:8183, chromium:927746
Reviewed-on: https://chromium-review.googlesource.com/c/1451879
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Jaroslav Sevcik <jarin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59344}