Request proper features in spirv_asembly tests

Request proper features in spirv_asembly tests

image_sampler and ubo_padding tests used stores to SSBOs without
requesting proper features. In this change implementation of
ShaderTestUtil was modified to enable possibility to create test
for individual stages. Now proper features could be requested
before performing the tests for specified stages.

Components: Vulkan

VK-GL-CTS issue: 1049

Affects:
dEQP-VK.spirv_assembly.instruction.graphics.image_sampler.*
dEQP-VK.spirv_assembly.instruction.graphics.ubo_padding.*
dEQP-VK.spirv_assembly.instruction.graphics.*

Change-Id: I03441b385097340faa72b18e17f09a07eba49efb