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Fix T89984: Improve Icon previews reflective and transmissive materials.

Before this commit rendering material icons the floor will is hidden.
This reduces the readability of reflective/refractive materials.

check patch for additional screenshots and notes.

This patch will switch the floor material that uses ray visibility tricks to render a floor for reflective rays.

Eevee uses screen space reflections that makes this a different problem. There is nothing else drawn in
the scene in screen space so we need a different trick. Using math we convert a reflective ray to UV space
and generate a world that projects a checker pattern to infinity.

As now the floor is in the world it is being reflected via
a cubemap. As the film is transparent the background (including the floor isn't rendered)

In the future when Eevee supports vulkan raytracing we can re-evaluate and perhaps remove this
approximation.

We tried lightprobes but that wasn't able to do the trick.
Using the compositor would lead to more memory usage (render layers and intermediate buffers) and slower performance.
Solution has been validated with Simon

Reviewed By: sybren, Severin

Differential Revision: https://developer.blender.org/D11988