Emulate sampler lod bias

[aitor-lunarg]

#2142 tries to tackle this issue exposing internal Metal SPIs. Unfortunately, even with MVK_USE_METAL_PRIVATE_API enabled, there are still CTS tests failing in the M3 chip family. Proposed solution is to emulate as pointed out in #2142 (comment)

Failing CTS tests:

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

[aitor-lunarg]

I think it would be beneficial to rework how samplers are passed to Metal so that we pass the following data per sampler:

• sampler
• bias
• border_color

Then modify the shader to add bias (since bias is implemented in shader for Metal) and handle opaque black and as a nice side effect support custom border color (unsure if MoltenVK has support for this, I think not).

Refer to KhronosGroup/Vulkan-Portability#37 (comment) for the custom border color.

Mentioning this because it could be a unified effort to support bias and border color since both require similar changes.