Fix issues in load_store_op_none tests
This commit fixes several issues from the load_store_op_none tests:
- Checking depth/stencil image format support in a checkSupport() method
instead of at iteration time.
- Validation error regarding mismatched attachment counts in dynamic
rendering variants.
- Validation error regarding image layout in dynamic rendering variants.
- Wrong barriers after clearing color and depth/stencil images.
- Make the code not assume depth/stencil formats have both aspects,
paving the way to testing more formats in the near future.
Affected tests:
dEQP-VK.*.load_store_op_none.*
Components: Vulkan
VK-GL-CTS issue: 3413
Change-Id: Iec237547f5762f299f1225eb4dda010e4256b367