Add tests checking max varyings per shader stage

Add tests checking max varyings per shader stage

It adds tests for checking that shaders defining the maximum number
of shader input/output components work as expected.

This patch doesn't test tessellation and geometry shader inputs.

Added tests:

dEQP-VK.pipeline.max_varyings.*

Components: Vulkan
VK-GL-CTS issue: 71

Change-Id: Id6528493ce2048d510365f030478934eaba9ad33