This is essentially a stripped down version of FHardwareTexture, which can exist on the API independent size, and which stores pointers to hardware textures instead of OpenGL texture handles.
This will mostly ensure that each patch used for composition is only loaded once and automatically unloaded once no longer needed.
So far only for paletted rendering, but the same logic can be used for true color as well.
* split up FMultiPatchTexture into a builder class and the actual image source.
* since images can now be referenced by multiple textures the old redirection mechanism has been removed. It can be done better and less intrusive now. Simple single patch textures already directly reference the underlying patch image now.
* allocate all image source related data from a memory arena. Since this is all static this makes it a lot easier to free this in bulk.
This was done to make reviewing easier, again because it is virtually impossible to search for the operators in the code.
Going through this revealed quite a few places where texture animations were on but shouldn't and even more places that did not check PASLVERS, although they were preparing some paletted rendering.
This class has only meaning for software-based warping so it doesn't have to be a part of the FTexture hierarchy.
Making it a subclass of FSoftwareTexture is fully sufficient.
This reuses the FTexCoordInfo class the hardware renderer had been using to calculate wall texture offsetting.
The software renderers still need this sorted out to bring them in line with the rest of the code, though, but they do not have this code sufficiently well organized to make this a straightforward task.
This was a relic from trying to support ZDoomGL's texture shader system but would make texture management with Vulkan significantly more complicated because it would require dynamic descriptor set management for textures which can cause a lot of overhead.
Decals will now be processed into a list in the processing pass, allowing to use the vertex buffer even on GL3 hardware and to offload this part of the work to a multithreaded worker task.
