Add coverage for stencil image sampling

Add coverage for stencil image sampling

Add tests for sampling using nearest filter from following
stencil image formats: VK_FORMAT_S8_UINT, VK_FORMAT_D24_UNORM_S8_UINT,
VK_FORMAT_D32_SFLOAT_S8_UINT.

New tests:
dEQP-VK.texture.filtering.2d.formats.s8_uint.nearest
dEQP-VK.texture.filtering.2d.formats.d24_unorm_s8_uint_stencil.nearest
dEQP-VK.texture.filtering.2d.formats.d32_sfloat_s8_uint_stencil.nearest
dEQP-VK.texture.filtering.unnormal.formats.s8_uint.nearest
dEQP-VK.texture.filtering.unnormal.formats.d24_unorm_s8_uint_stencil.nearest
dEQP-VK.texture.filtering.unnormal.formats.d32_sfloat_s8_uint_stencil.nearest
dEQP-VK.texture.filtering.cube.formats.s8_uint.nearest
dEQP-VK.texture.filtering.cube.formats.d24_unorm_s8_uint_stencil.nearest
dEQP-VK.texture.filtering.cube.formats.d32_sfloat_s8_uint_stencil.nearest
dEQP-VK.texture.filtering.2d_array.formats.s8_uint.s8_uint_nearest
dEQP-VK.texture.filtering.2d_array.formats.d24_unorm_s8_uint_stencil.d24_unorm_s8_uint_stencil_nearest
dEQP-VK.texture.filtering.2d_array.formats.d32_sfloat_s8_uint_stencil.d32_sfloat_s8_uint_stencil_nearest
dEQP-VK.texture.filtering.3d.formats.s8_uint.s8_uint_nearest
dEQP-VK.texture.filtering.3d.formats.d24_unorm_s8_uint_stencil.d24_unorm_s8_uint_stencil_nearest
dEQP-VK.texture.filtering.3d.formats.d32_sfloat_s8_uint_stencil.d32_sfloat_s8_uint_stencil_nearest

Components: Vulkan

VK-GL-CTS issue: 2048

Change-Id: I43f28e6ec4eee5c04e444c9cded1c0a15b3d5e4c