Move tests under package directory

.github/workflows/ci.yml

.gitlab-ci.yml

pytools/log.py

pytools/test/test_data_table.py

pytools/test/test_graph_tools.py

pytools/test/test_math_stuff.py

pytools/test/test_mpi.py

pytools/test/test_persistent_dict.py

pytools/test/test_py_codegen.py

pytools/test/test_pytools.py