They're done using the pattern shader.
The pattern shader now gained a stack where vec4's can be pushed and
popped back later, which allows storing the position before computing
the new position inside the repeat node's child.
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.
Add a bunch of inline functions for graphene_rectangle_t.
We use those quite extensively in tight loops so making them as fast as
possible via inlining has massive benefits.
The current render-heavy benchmark I am playing (th paris-30k in node-editor)
went from 49fps to 85fps on my AMD.
