Code modernization by clang-tidy

ProcessLib/CoupledSolutionsForStaggeredScheme.cpp

ProcessLib/HT/CreateHTProcess.cpp

ProcessLib/HT/HTProcess.cpp

ProcessLib/LocalAssemblerInterface.cpp

ProcessLib/Output.cpp

ProcessLib/Process.cpp

ProcessLib/ProcessOutput.cpp

ProcessLib/UncoupledProcessesTimeLoop.cpp

ProcessLib/VectorMatrixAssembler.cpp