class Utils::FileSystem -> namespace FileSystem

Core/InputOutput/OutputDataIOHelper.cpp

Core/Tools/FileSystem.cpp

Core/Tools/FileSystem.h

Tests/Functional/Core/CoreTest.cpp

Tests/Functional/Core/PolDWBAMagCylinders2.cpp

Tests/Functional/PyCore/export/PyExportTest.cpp

Tests/Functional/PyCore/persistence/PyPersistenceTest.cpp