Add test coverage of multi-plane IOSurfaces.

Bug: chromium:1115621
Change-Id: Ib2150c4221a3e49f01ab016cebba4830194ab2b5
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2376174Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Commit-Queue: Geoff Lang <geofflang@chromium.org>