Check write vertex support in descriptor indexing

Check write vertex support in descriptor indexing

The descriptor indexing tests which are intended to test vertex write
check if the vertexPipelineStoresAndAtomics feature is supported before
loading the descriptorIndexing_vertx_shaderWrites shader. The vertex
write verifcation needs the same check to ensure the verification is
not run when the shader is not present.

Affects: dEQP-VK.descriptor_indexing*

VK-GL-CTS Issue: 2013

Change-Id: I3870b95b65c0b657708788b9bd2a7adcb5bd8f3d
Components: Vulkan