The fuzzer instantiates the module twice: Once for reference
interpretation / execution, and once for the actual execution of
Liftoff/TurboFan code.
For some reason, the two code paths for interpretation and Liftoff
reference execution used different patterns: Interpretation was using
the first instance, and then creating a second instance for actual
execution, whereas the Liftoff path used a second instance for the
reference execution and used the first one for the actual execution.

This CL refactors this to always create a "reference instance" first,
use that for either the interpreter or Liftoff, and then create a second
instance for the actual execution.

R=thibaudm@chromium.org

Bug: v8:12425
Change-Id: I19754264240d8570f00161abb7aecba1cc2b2ae0
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3683323
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80900}