Terrain / 3D Tiles exaggeration

[j9liu]

Terrain + 3D Tiles exaggeration is a feature in CesiumJS that we do not yet have in our native runtimes. But it's been asked about a few times (e.g., on the forum here), so we should start tracking this.

Unity counterpart to https://github.com/CesiumGS/cesium-unreal/issues/353.

[JanikCodes]

bump as this would be a neat addition.