When executing wasm code for testing, we did not create a
WasmInstanceObject and link it to the generated code. This required
some special handling at runtime (mainly for stack trace generation).
This CL always provides the WasmInstanceObject, such that e.g. function
names can be resolved the usual way.
The module bytes referenced by the WasmCompiledModule linked with the
WasmInstanceObject do not hold a valid wasm module yet. Instead, we
just add the bytes we need, and make the objects in WasmModule point to
those bytes (currently only used for function names). Those bytes will
not be parsed at runtime anyway.

R=titzer@chromium.org
CC=jgruber@chromium.org
BUG=v8:5620

Review-Url: https://codereview.chromium.org/2551053002
Cr-Commit-Position: refs/heads/master@{#41809}