Anti-Aliasing refactor

[jukibom]

MSAA is pretty bad because it causes a bunch of silly issues which have to be worked around. That said, it's pretty good for VR. I'm not sure if the added code complexity is worth it though.

• [ ] Remove MSAA and all the weird hacks that are enabled when it's active
• [ ] Refactor out camera stacking - it's expensive. Replace with multi pass with culling.
  • [ ] Make sure this works in VR to draw the HUD still!
• [ ] Test out if a deferred rendering path has better performance without camera stacking
• [ ] Add options for FXAA and SMAA
• [ ] Add TAA if Unity backports this fix https://issuetracker.unity3d.com/issues/motion-vectors-are-incorrect-for-terrain-mesh-when-it-doesnt-use-a-default-transform (works everywhere but terrain, naturally)