Introduce new `SimulateMoves` and `SimulateSwaps` methods which take an initial
"state" as a FixedArray and perform a given list of moves on it. They give us
what the result of testing the CodeGenerator's AssembleMove and AssembleSwap
should be.

This way, we can now compare the results of running parallel moves with a
reference simulation.

Bug: v8:6848
Change-Id: I228f4310f32d2a82e0744afaff183e2c7ac08cb7
Reviewed-on: https://chromium-review.googlesource.com/723222
Commit-Queue: Pierre Langlois <pierre.langlois@arm.com>
Reviewed-by: Bill Budge <bbudge@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48656}