Bugfix: Use PointSize in draw tests

Bugfix: Use PointSize in draw tests

Tests that rasterize points have to write to PointSize variable.
Also fix nonCoherentAtomSize errors from validation.

Affected tests:
- dEQP-VK.draw.basic_draw.draw.point_list.*
- dEQP-VK.draw.basic_draw.draw_indexed.point_list.*
- dEQP-VK.draw.basic_draw.draw_indirect.point_list.*
- dEQP-VK.draw.basic_draw.draw_indexed_indirect.point_list.*
- dEQP-VK.draw.instanced.draw_vk_primitive_topology_point_list
- dEQP-VK.draw.instanced.draw_indexed_vk_primitive_topology_point_list
- dEQP-VK.draw.instanced.draw_indirect_vk_primitive_topology_point_list
- dEQP-VK.draw.instanced.draw_indexed_indirect_vk_primitive_topology_point_list

Fixes #536

Change-Id: Ief9df51887babfc3765b0d11c6431765f322c634