Multi-Frame Rendering

[Wunkolo]

Basalt plugins have a pretty good pattern of MFR rendering on top of vulkan, but I want vulkanator to ultimately use something better.

The easiest way to have MFR implemented is to give each SmartRender context its own: CommandPool, DescriptorPool, DescriptorSet, and DeviceMemory for both the Input and Output and Uniforms. This is likely what "version 1" will have.

The improved pattern will utilize a pool of each type that is recycled and protected using a global VK_KHR_timeline_semaphore(Core in Vulkan 1.2) to indicate when a particular entry in each pool is available for re-use or not and allocating a new element in the case that all entries are in-use. This allows for resource allocation to scale with the amount of data that can be processed and acts as a sort of swapchain of GPU resources, scaling only by as fast as the system can let go of resources. A faster processor and GPU will have wide resource-pools. A slower and more serial processor and GPU will have narrower slots.

MoltenVK supports VK_KHR_timeline_semaphore KhronosGroup/MoltenVK#1124 and can safely utilize this pattern as well.