Test separate and combined images and samplers in SPIR-V

Test separate and combined images and samplers in SPIR-V

Tests were added to verify that the following Image Instructions
work with related descriptor types in all possible shader stages:

OpImageRead
- Storage image

OpImageFetch
- Sampled image with separate sampler
- Combined image sampler

OpImageSampleExplicitLod
- Sampled image with separate sampler
- Combined image sampler

The following scenarios are covered to verify that images and samplers
work as function parameters and that you can combine an image and a
sampler both before and after passing it into a function.

- Use image and sampler as local variables
- Pass image to function
- Pass sampler to function
- Pass image and sampler to function

New tests:

dEQP-VK.spirv_assembly.instruction.graphics.image_sampler.*
dEQP-VK.spirv_assembly.instruction.compute.image_sampler.*

Components: Vulkan

VK-GL-CTS issue: 104

Change-Id: I1de35fc0099881b3242f6e953a5c9624004e0f3e