I tried to use real multisampling but the main problem is the outline detection that needs to have matching depth samples.
So adding FXAA instead. Always on for now, may add a parameter for it later.
One thing to note is that we need to copy the final output once again to the main color buffer because we cannot swap the dtxl textures (they can be referenced elsewhere like GPUOffscreen).
We could improve upon this and add TAA on top if viewport is still.
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