WIP cl_ext_image_tiling_control test plan

[kpet]

Starting to capture test scenarios for https://github.com/KhronosGroup/OpenCL-Docs/pull/710

Image creation

TBD

Image creation from buffer

TBD

Image creation from external memory

• CL_IMAGE_TILING_LINEAR_EXT
• CL_IMAGE_TILING_OPTIMAL_EXT is never allowed when importing
• TODO: mechanism to infer tiling when possible/allowed