Support the VK_EXT_pipeline_creation_feedback extension.

[cdavis5e]

This provides feedback that indicates:

• how long it took to compile each shader stage and the pipeline as a whole;
• whether or not the pipeline or any shader stage were found in any supplied pipeline cache; and
• whether or not any supplied base pipeline were used to accelerate pipeline creation.

This is similar to the performance statistics that MoltenVK already collects.

Since we don't use any supplied base pipeline at all, this implementation never sets
VK_PIPELINE_CREATION_FEEDBACK_BASE_PIPELINE_ACCELERATION_BIT. However, I've identified several places where we could probably use the base pipeline to accelerate pipeline creation. One day, I should probably implement that.

Likewise, because we don't yet support using MTLBinaryArchives, VK_PIPELINE_CREATION_FEEDBACK_APPLICATION_PIPELINE_CACHE_HIT_BIT is never set on the whole pipeline, though it is set for individual stages, on the assumption that any shader found in a cache is likely to be found in Metal's own implicit cache.

In this implementation, shader stage compilation time includes any time needed to build the MTLComputePipelineStates needed for vertex and tessellation control shaders in tessellated pipelines.

This patch also changes compilation of the vertex stage MTLComputePipelineStates in tessellated pipelines to be eager instead of lazy. We really ought to have been doing this anyway, in order to report pipeline failures at creation time instead of draw time. I'm not happy, though, that we now pay the cost of all three pipeline states all the time, instead of just the ones that are used.

This also gets rid of some fields of MVKGraphicsPipeline that were only used during pipeline construction, which should save some memory, particularly for apps that create lots of pipelines.

[cdavis5e]

@AntarticCoder Heads up--when you implement VK_KHR_ray_tracing_pipeline, you'll now need to support this as well.

[AntarticCoder]

Thanks I'll keep that in mind

[billhollings]

Thanks for doing this. LGTM. Just one quibble about some repetitive code pasting.

[billhollings]

Thanks. LGTM.

mvkGetElapsedNanoseconds() - Nice. Much more appropriate than the name than I had suggested.