Don't filter out some VK_NV extensions used in tests

Don't filter out some VK_NV extensions used in tests

The following extensions are referenced by extisting tests,
but that are hidden and appear to be unavailable:
- VK_NV_clip_space_w_scaling
- VK_NV_scissor_exclusive
- VK_NV_shading_rate_image

This CL unhides those extension. There is also a minor bug fix for the
dEQP-VK.dynamic_state.*.viewport_coarse_sample_order_nv.* tests to fix the
invalid usage of the VkCoarseSampleOrderCustomNV struct.

Affects:

dEQP-VK.dynamic_state.*.viewport_w_scaling_nv.*
dEQP-VK.dynamic_state.*.viewport_shading_rate_palette_nv.*
dEQP-VK.dynamic_state.*.viewport_coarse_sample_order_nv.*
dEQP-VK.dynamic_state.*.exclusive_scissor_nv.*

Components: Vulkan

VK-GL-CTS issue: 3481

Change-Id: I7a48d3f05e5710bd53cd4c3f86c61ba912bf91be