custom piecewise change test in KSP

[ragusa]

add this idea into modern PETSc/KSP framework

https://github.com/chi-tech/chi-tech/blob/5f54abe3a1457e5a546043da9ce67c42696467c4/ChiModules/LinearBoltzmannSolver/IterativeOperations/lbs_compute_pwchange.cc

[wdhawkins]

I'm not sure there is anything to do here. We could modify our custom piecewise convergence routine to be more "PETSc-like", but, as far as I can tell, we're still going to need a custom convergence callback.