Retain upscaling pipeline

[IceSentry]

Objective

• On most frames the upscaling pipeline doesn't change but this code was made before the retained render world and inserted a new one every frame

Solution

• Retain the upscaling pipeline and only update it if necessary

Testing

• I tested the split_screen example and things still work as expected

Notes

Realistically, the performance difference will be minimal since all the heavy work is already cached but that still allows us to skip a couple of validation steps and a blocking function.

[Smerom]

I lack knowledge of the rendering pipeline, but the code looks correct.