This is to prepare larger refactorings that reduce the amount of
information stored in the WasmCompilationUnits and avoid ever storing
the ModuleEnv. Instead, we will generate it when needed. This will
allow us to correctly switch from a trap-handler configuration to
non-trap-handler.

R=mstarzinger@chromium.org

Bug: v8:8343, v8:5277
Change-Id: I383a8105448ccdcae1148ddfebd74db70c648ecf
Reviewed-on: https://chromium-review.googlesource.com/c/1293951Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56893}