The {WasmSharedModuleData} struct was introduced to hold data common to
all wasm instances belonging to the same module. The idea was to keep
"internal state" separate from the JS-facing {WasmModuleObject}. Since
this objective has no real value, and we already store some internal
data on the {WasmModuleObject}, this CL merges these two objects.

R=titzer@chromium.org, mstarzinger@chromium.org

Bug: v8:7754
Cq-Include-Trybots: luci.chromium.try:linux_chromium_rel_ng
Change-Id: I04f6d07bf5d812bc4717af26f0f64231345861f9
Reviewed-on: https://chromium-review.googlesource.com/1097491
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53698}