This is part of the effort to consolidate the ownership of
wasm instantiation/specialization parameters.

This change is focused solely on the interpreter part of that effort, to
verify we're not regressing performance in interpreter benchmarks.

There are two aspects being addressed:
- dataflow-wise, we always fetch the interpreter's memory view from the
runtime objects (i.e. WasmInstanceObject/WasmCompiledModule). This is
consistent with how other instance-specific information is obtained
(e.g. code, indirect functions).

- representation-wise, we do not reuse ModuleEnv/WasmInstance just for
the memory view, because it is surprising that other instance info isn't
accessed from there. 

Bug: 
Change-Id: I536fbffd8e1f142a315fa1770ba9b08319f56a8e
Reviewed-on: https://chromium-review.googlesource.com/602083Reviewed-by: Ben Titzer <titzer@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47205}