New ICP variant (Symmetric Objective Function for ICP)

[warmist]

There is a new ICP variant with minimal changes from PointToPlane variant. Afaik it only needs to have new classes and two functions changed in a new pcl::registration::TransformationEstimation<??>.

All the details in this paper: https://gfx.cs.princeton.edu/pubs/Rusinkiewicz_2019_ASO/symm_icp.pdf