Restructure copy image test iterations
Restructure copy image test iterations

Packing test iterations so that work per buffer swap is maximized
without running the risk of hitting per-iteration timeout. Yields
execution time drops of roughly 50% on at least 2 GPU architectures.

Bug: 33965234
Test: Copy image tests on multiple devices and L MR1 N9 for detection capability.
Change-Id: I7de5231da0d8a1d2bd22ec3741f1481e2ebd5475

KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,KhronosGroup/Vulkan-CTS,googlestadia/VK-GL-CTS,KhronosGroup/VK-GL-CTS,googlestadia/VK-GL-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,KhronosGroup/Vulkan-CTS,chadversary/deqp,googlestadia/VK-GL-CTS,chadversary/deqp,KhronosGroup/VK-GL-CTS