Add shaderStorageImage{Read|Write}WithoutFormat tests

Add shaderStorageImage{Read|Write}WithoutFormat tests

This adds new store tests that remove the format layout qualifier
from the writeonly image and new load_store tests that remove
the format layout qualifier from the readonly image.

Since we don't have access to the physical device properties
during shader program compilation, we follow the same approach
of other tests and write two variants of the shader, one that
declares the format qualifier and one that doesn't. We use a
test flag to track if a specific test case is intended to check
behavior with or without image format layout qualifiers declared,
and use that to decide the shader variant to use at run-time.

The original tests now live under
dEQP-VK.image.{load_}store.with_format.* and the new tests
are added under dEQP-VK.image.{load_}store.without_format.*

Components: Vulkan
VK-GL-CTS issue: 164

New tests:
dEQP-VK.image.store.without_format.*
dEQP-VK.image.load_store.without_format.*

Change-Id: I15d7b7e8dafd4e229ff23f61700580b60cb29cb0