Allow CoveredSurfaceOnBody to Use User‑Defined Mesh Coordinates

Currently, Oresium’s CoveredSurfaceOnBody relies on the satellite Field of View to determine the meshes used to display the surface covered by the satellite.

While this approach works well in many cases, it tightly couples the surface representation to the FOV computation.

I suggest allowing users to provide their own predefined mesh coordinates for CoveredSurfaceOnBody, instead of always deriving them from the satellite FOV.

This would give users more flexibility, especially for advanced visualization use cases, precomputed coverage areas, or custom geometries that are not directly tied to the instantaneous FOV.