In this format it will be a lot easier to iterate on this since adding
and removing pipelines only has to be done in a single place.
This commit also separates out the main background color from individual
cell background color drawing, because sometimes kitty images need to be
between the main background and individual cell backgrounds (kitty image
z-index seems to be entirely broken at the moment, I intend to fix it in
future commits).
The code in metal/image.zig and opengl/image.zig was virtually identical
save for the texture options, so I've moved that to the GraphicsAPI and
unified them in to renderer/image.zig
These should not be independent per-frame, that makes the time
calculations all sorts of jank.
Also moves the uniforms struct layout in to `shadertoy.zig` and cleans
up the handling in general somewhat.
This commit is very large, representing about a month of work with many
interdependent changes that don't separate cleanly in to atomic commits.
The main change here is unifying the renderer logic to a single generic
renderer, implemented on top of an abstraction layer over OpenGL/Metal.
I'll write a more complete summary of the changes in the description of
the PR.
