Enforce the usage of new style cost functionals

[sblauth]

Also closes #133

[codecov-commenter]

Codecov Report

Merging #134 (14422b8) into main (fb86934) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main     #134      +/-   ##
==========================================
- Coverage   93.75%   93.74%   -0.00%     
==========================================
  Files          65       65              
  Lines        5628     5625       -3     
==========================================
- Hits         5276     5273       -3     
  Misses        352      352              

Impacted Files	Coverage Δ
...ization/optimal_control/optimal_control_problem.py	100.00% <ø> (ø)
...n/shape_optimization/shape_optimization_problem.py	96.95% <ø> (ø)
cashocs/space_mapping/optimal_control.py	89.21% <ø> (ø)
cashocs/space_mapping/shape_optimization.py	85.59% <ø> (ø)
cashocs/_constraints/constrained_problems.py	92.86% <100.00%> (ø)
cashocs/_constraints/solvers.py	94.39% <100.00%> (+0.03%)	⬆️
cashocs/_optimization/optimization_problem.py	94.41% <100.00%> (-0.15%)	⬇️

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