PointNet Lifting (Pointcloud to Hypergraph)

This lifting generates a hypergraph by mimicking the set abstraction layer of PointNet++. This is done by farthest point sampling and subsequent clustering of points within a radius of the sub-sampled points. These clusters then constitute hyperedges which can be used to pool information from local neighbourhoods. Constructing a complete PointNet++ from this would require us to recursively apply the lifting while regarding the previous hyperedges as the new nodes (probably currently not supported by the code base).

From https://github.com/pyt-team/challenge-icml-2024/pull/53