[SPIRV][DirectX] Add variable rate shading

[inbelic]

Required for testing of SV_ShadingRate.

Current status: No support.

The first step will be to refine the following acceptance criteria for refinement/estimation.

Note: The scope here is tier to allow specification at the pipeline and vertex shader output. We don't need to consider screen-space image. See here for more details.

A choice for scope is to determine if we would like the shading rate combiner to be variable.

AC:

• Add query for the required feature support (D3D12_VARIABLE_SHADING_RATE_TIER, VK_KHR_fragment_shading_rate)
• Allow YAML test configuration to specify the coarseness (1x1, 1x2, ... , 4x4) and combiner (if included in scope)
• DX: Ensure RSSetShadingRate is called with explicit configuration
• SPV: Ensure VkPipelineFragmentShadingRateStateCreateInfoKHR is configured
• Add independent testing of functionality