MoltenVK Vulkan 1.0: Texture LOD selection for 2D with height 1

[aitor-lunarg]

Failing CTS tests:

dEQP-VK.pipeline.monolithic.sampler.max_sampler_lod_bias.sampler_bias
dEQP-VK.pipeline.monolithic.sampler.max_sampler_lod_bias.shader_bias

Investigation results: Required MoltenVK fix for sampler_bias variant KhronosGroup/MoltenVK#2163 and suspicion that Metal may be incorrectly selecting the texture LOD for sampling when texture is 2D with height 1.

Reasoning:
Test creates a 2D texture with dimensions (max_width, 1, 1) for sampling and a 2D texture with dimentions (1, 1, 1) as render target. Explanation will focus on shader_bias since that's the one correctly working from MoltenVK's end. Without changes to the test, the sampled mip level will be the last one. However, if we increase the render target texture dimensions to be the same as the sampled texture, the test passes. Modifying the render target dimensions to other values in between for width and height, we see that the sampled mip will vary.

Proposed solution: I would like to test a few more things before discarding the issue as a Metal bug. I will revisit this later once all CTS failures are triaged.

cc/ @billhollings