tests: Bugfix check and add mip copy tests
tests: Bugfix check and add mip copy tests

Fixed a bug in the buffer size calculation for compressed mip levels
when copying less than a full block at the perimeter. Added a set of
validation tests that exercise copies in/out of mip levels of
compressed textures. Added an image init() fxn to the test framework
that takes an imageCreateInfo input, to allow full control of image
varieties.

Change-Id: I240ed6e1f45889e58b759f8f261392725dadb498

KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools,KhronosGroup/Vulkan-Tools