Reduce renderer state swaps

[ArthurVoxowl]

Sub-tasks to work towards reducing state swaps, which is one major component of our CPU usage each frame,

• [x] Reduce shader variants
  • [x] Quads https://github.com/voxowl/particubes-private/pull/4739
  • [x] Shapes https://github.com/voxowl/particubes-private/pull/5078
• [ ] Reduce number of framebuffers
  • [x] Pipeline buffers https://github.com/voxowl/particubes-private/pull/4875
  • [ ] Atlased shadowmaps
• [ ] Harmonize shaders input/output within each pipeline
• [ ] Harmonize vertex layouts