Add Ability to Determine Implicit Roughness from LOD0 as Normal Offset

[Mr4Goosey]

It'd be interesting to explore the potential of using the implicit roughness from a generator at LOD0 to 'roughen' the vertex normals of distant terrain on higher LODs.
Distant voxel landscapes quickly become a very smooth blob, and they would likely benefit a lot from simply having rougher vertex normals, or alternatively a vertex property passed into the material so the user can manually modulate the surface normals or roughness there. Akin to Toksvig offsets.