Tidy up tolerance in NekLinSystIter and NekNonlinSysIter solvers

CHANGELOG.md

library/Demos/LibUtilities/LinSysIterDemo.cpp

library/Demos/LibUtilities/NonlinSysIterDemo.cpp

library/LibUtilities/CMakeLists.txt

library/LibUtilities/LinearAlgebra/NekLinSysIter.cpp

library/LibUtilities/LinearAlgebra/NekLinSysIter.h

library/LibUtilities/LinearAlgebra/NekLinSysIterCG.cpp

library/LibUtilities/LinearAlgebra/NekLinSysIterCG.h

library/LibUtilities/LinearAlgebra/NekLinSysIterCGLoc.cpp

library/LibUtilities/LinearAlgebra/NekLinSysIterCGLoc.h

...Utilities/LinearAlgebra/NekLinSysIterFixedpointJacobi.cpp

...ibUtilities/LinearAlgebra/NekLinSysIterFixedpointJacobi.h

library/LibUtilities/LinearAlgebra/NekLinSysIterGMRES.cpp

library/LibUtilities/LinearAlgebra/NekLinSysIterGMRES.h

library/LibUtilities/LinearAlgebra/NekLinSysIterGMRESLoc.cpp

library/LibUtilities/LinearAlgebra/NekLinSysIterGMRESLoc.h

library/LibUtilities/LinearAlgebra/NekNonlinSysIter.cpp

library/LibUtilities/LinearAlgebra/NekNonlinSysIter.h

...ary/LibUtilities/LinearAlgebra/NekNonlinSysIterNewton.cpp

library/LibUtilities/LinearAlgebra/NekNonlinSysIterNewton.h