In the case where descriptor indexing is not enabled and the number of
max images is small (or we use extensive amounts of immutable samplers),
we need to be able to switch descriptors.
This patch makes that possible.
This allows having different layouts sothat we can support immutable
samplers, whcih are required for multiplane and YUV formats.
We don't use them yet.
Because GL flips its shit sometimes (ie when it's the framebuffer),
pass the height of the target as the flip variable, so commands
that need to operate on the pixels can flip the y axis around this value.
This heaves over an inital chunk of code from the Vulkan renderer to
execute shaders.
The only shader that exists for now is a shader that draws a single
texture.
We use that to replace the blit op we were doing before.
