This removes the last embedded objects from {WasmCode} objects. We still
embedded the {undefined} value into Wasm-to-JS wrappers, those are now
loaded from the instance object similar to {null} values. The relocation
information for {WasmCode} now no longer contains {EMBEDDED_OBJECT} as
entries anywhere. Another step towards making code Isolate independent.

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

Change-Id: I720cd0230948f2063770595ceded373d9bb1e87d
Reviewed-on: https://chromium-review.googlesource.com/1075268
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Ben Titzer <titzer@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53408}