Prefix libraries VoxelGridCore and VoxelGrids with VisionX?

The libraries VoxelGridCore and VoxelGrids may be to generic, or it may be not clear where they reside when linking them in another project (or may cause name clashes). Should we rename them to VisionXVoxelGridCore and VisionXVoxelGrids? (Would be similar to VisionXPointCloud.)

If no one is using them right now (they are rather new), we can just safely rename them in their CMakeLists.txt. Otherwise, people have to update their cmake files.