Move all test files in the tests directory

src/pymatlib/core/cpp/CMakeLists.txt

src/pymatlib/core/test_interpolate_functs_perf.py

tests/cpp/CMakeLists.txt

tests/cpp/TestArrayContainer.py

tests/cpp/test_interpolation.cpp

tests/legacy/__init__.py

tests/legacy/test_interpolate_functs_perf.py

tests/python/__init__.py

tests/python/test_alloy.py

tests/python/test_assignment_converter.py

tests/python/test_data_handler.py

tests/python/test_interpolation.py

tests/python/test_interpolators.py

tests/python/test_models.py

tests/python/test_typedefs.py

tests/python/test_yaml_config.py