Add advanced refractions

[GSterbrant]

Description

Refractions currently only takes into account the environment reflections, which gives an underwhelming impression of refractive surfaces, see #4437 for an example.

In order to fix this, we need to consider the world space position of the point of refraction, as well as the refraction vector in order to accurately sample from the background, and also provide a fallback for when the refraction vector goes out of bounds.