This removes the last reference from {NativeModule} that made it
specific to a concrete WebAssembly instance, by only referencing the
{WasmSharedModuleData} instead of a {WasmCompiledModule}. Note that
eventually we want to remove this reference completely to become even
independent of the underlying Isolate soon.

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

Change-Id: I29b8cde8beadeef75c90e90fbff1830f2bf4e636
Reviewed-on: https://chromium-review.googlesource.com/1032433
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52853}