Move out all serialization related tests to
{test-wasm-serialization.cc}, to reduce the size of
{test-run-wasm-module.cc}.

R=titzer@chromium.org

Bug: v8:7754
Change-Id: I0b2133baf69e2557df27d1733cc267d1d4cf7452
Reviewed-on: https://chromium-review.googlesource.com/1107980Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53909}