No new tests or any changes, just moving to a separate file in
preparation for adding lots more of these tests soon.
Change-Id: Iaa7eef52384e702c395a6db312fef19e22507644
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/63580
Kokoro: Kokoro <noreply+kokoro@google.com>
Auto-Submit: James Price <jrprice@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: James Price <jrprice@google.com>