Test multiple interpolations in a shader stage

Test multiple interpolations in a shader stage

Add tests for rendering simultaneously into multiple attachments using
different interpolation decorations. Verify result by rendering with
only one interpolation and attachment at a time. Check that each result
matches only with the reference frame using the same interpolation
decoration, with the exception of smooth and centroid without
multisampling.

New tests:
dEQP-VK.draw.multiple_interpolation.*

Components: Vulkan
VK-GL-CTS issue: 1110

Change-Id: I55ca7fad937b29e81512b0ee100ca8e811b7cf73