This avoids serializing and deserializing the sharable part of a module
when it is transferred via {TransferrableModule}, which is possible when
all Isolates run off the same engine via the --wasm-shared-engine flag.

This adds a new --wasm-shared-code flag to enable this feature.

R=ahaas@chromium.org
BUG=v8:7424

Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I099d581d7ccc4d058a4646f545a011745fd84eb4
Reviewed-on: https://chromium-review.googlesource.com/1142144
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#54806}