Fix issues in load_store_op_none tests

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