Introduce SumFunctionalConstrainedLinearization

Previously, the brittle-fracture program used a taylor-made linearization called ElasticEnergyConstrainedLinearization. However, there wasn't actually anything elasticity-specific in the code, and therefore this MR replaces said class by a generic SumFunctionalConstrainedLinearization.

dune/fracture-phasefields/sumfunctionalconstrainedlinearization.hh

 #ifndef DUNE_FRACTUREPHASEFIELDS_SUMFUNCTIONALCONSTRAINEDLINEARIZATION_HH
 #define DUNE_FRACTUREPHASEFIELDS_SUMFUNCTIONALCONSTRAINEDLINEARIZATION_HH
 
+#include <tuple>
+
+#include <dune/common/hybridutilities.hh>
+
+#include <dune/solvers/common/resize.hh>
+
 namespace Dune::FracturePhasefields {
 
 /**