This does not work with a setup where the same backend is driving both renderers.
Most of this is now routed through 'screen', and the decision between renderers has to be made inside the actual render functions.
The software renderer is still driven by a thin opaque interface to keep it mostly an isolated module.
The old organization made sense when ZDoom still was a thing but now it'd be better if all pure data with no dependence on renderer implementation details was moved out.
A separation between GL2 and GL3+4 renderers looks to be inevitable and the more data is out of the renderer when that happens, the better.
- moved testcolor and test fades into SWRenderer files.
These CCMDs work by hacking the default colormap and were never implemented for hardware rendering because they require many checks throughout the code.
Removing this made me realize that calling the renderers' FakeFlat functions from the automap is inherently unsafe with the recent refactorings because there is absolutely no guarantee that the data may actually still be defined when the automap is being drawn.
So the best approach here is to give the automap its own FakeFlat function that runs independently of render data and assumptions of data preservation. This one can also be a lot simpler because it only needs the floor, not the ceiling info.
Since the true color software renderer also handles them there is no point keeping them on the GL side.
This also optimized how they are stored, because we no longer need to be aware of a base engine which doesn't have them.
