This makes sure no underlying ArrayBuffer is reserved for modules that
don't declare a module. For the case where a memory is declared but the
initial size is 0, we still reserve a buffer in case of trap handlers.

R=ahaas@chromium.org
BUG=v8:9678

Change-Id: I837b8f257b63eb4111646806b899074babd7c9f7
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1784290Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#63568}