Add GSK_GPU_IMAGE_RENDERABLE and GSK_GPU_IMAGE_FILTERABLE and make sure
to check formats for this feature.
This requires reorganizing code to actually do this work instead of just
pretending formats are supported.
This fixes GLES upload tests with NGL.
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.
For now, it just renders using cairo, uploads the result to the GPU,
blits it onto the framebuffer and then is happy.
But it can do that using Vulkan and using GL (no idea which version).
The most important thing still missing is shaders.
It also has a bunch of copy/paste from the Vulkan renderer that isn't
used yet.
But I didn't want to rip it out and then try to copy it back later
