[All] Rename tools folder to utils

CMakeLists.txt

benchmark/timings-cholesky.cpp

benchmark/timings-derivatives.cpp

benchmark/timings-eigen.cpp

benchmark/timings-geometry.cpp

benchmark/timings.cpp

src/multibody/data.hpp

src/multibody/data.hxx

src/multibody/joint/joint-prismatic.hpp

src/multibody/joint/joint-revolute.hpp

src/multibody/model.hpp

src/multibody/model.hxx

src/parsers/utils.hpp

src/utils/axis-label.hpp

src/utils/file-explorer.hpp

src/utils/string-generator.hpp

src/utils/timer.hpp

unittest/aba.cpp

unittest/centroidal.cpp

unittest/cholesky.cpp