get row from itk matrix

just trying to update some code for more recent itk version (latest release)

Type definitions:

Things that don’t compile b/c they use old vnl types:

But - in brief - this is a question of how to replace old vnl operations with whatever is the right way to do wrt recent ITK.

Unfortunately, we still use VNL under the hood for Matrix. We want to transition to Eigen, but it is a large refactoring and no one has taken it up so far.