Allow Cartographic Polygon points to be specified as Longitude/Latitude/Height or ECEF instead of UE coordinates

[kring]

In many cases, it's convenient to define polygons using globe-oriented coordinates rather than using Unreal coordinates (which are then mapped to the globe by the CesiumGeoreference). It's currently possible to do this programmatically by using functions on the CesiumGeoreference to convert globe coordinates to Unreal coordinates, but it's a hassle, and it needs to be redone if the georeference origin changes.

CC @AlbanBERGERET-Epic