Skip ubershader mode works the same as hybrid ubershaders in that the
shaders are compiled asynchronously. However, instead of using the
ubershader to draw the object, it skips it entirely until the
specialized shader is made available.
This mode will likely result in broken effects where a game creates an
EFB copy, and does not redraw it every frame. Therefore, it is not a
recommended option, however, it may result in better performance on
low-end systems.
This could happen because the vertex memory was already committed, if a
uniform buffer allocation failed and caused a command buffer to be
executed, it would be associated with the previous command buffer rather
than the buffer containing the draw that consumed these vertices.
There's not a lot of point in passing these around or storing them
(texture cache/state tracker mainly) as there will only ever be a single
instance of the class.
Also adds downcast helpers such as Vulkan::Renderer::GetInstance().
