Use mandatory formats in stencil export tests

Use mandatory formats in stencil export tests

Stencil export tests were using VK_FORMAT_S8_UINT, which is not a
mandatory format. This commit adds more test variants using mandatory
stencil image formats for 2D images, guaranteeing these tests can run on
more implementations.

Existing tests have been renamed and other variants have been added.

Affected and new tests:
dEQP-VK.pipeline.shader_stencil_export.*

Components: Vulkan
VK-GL-CTS issue: 2292

Change-Id: Ied82c9958d3126fcb1b72716b3c4fdc109fe2e87