This avoids creating an on-heap copy for import wrappers by directly
adding the {WasmCode} into the native heap instead. It reduces
compilation time as well as useless GC pressure.

R=clemensh@chromium.org
BUG=v8:8423

Change-Id: Ia063523834c963591027c7d1ed78b795d24907bf
Reviewed-on: https://chromium-review.googlesource.com/c/1335566
Commit-Queue: Michael Starzinger <mstarzinger@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Reviewed-by: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#57511}