This funnels all serialization and deserialization calls through the
common interface in the wasm-serialization.h file. All call sites are
now uniform, independent of the --wasm-jit-to-native feature.

R=titzer@chromium.org
BUG=v8:6876

Cq-Include-Trybots: master.tryserver.chromium.linux:linux_chromium_rel_ng
Change-Id: I105907acfeba4b0e277b2003d099c5db6ab59dd3
Reviewed-on: https://chromium-review.googlesource.com/860042Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#50501}