Rename test_utils subpackage and test_utils/test_comms.py to avoid pytest conflicts

[vyasr]

pytest will assume that any file or directory named test_* is a test (see pytest's discovery rules). wholegraph currently puts testing utilities into a file that fits this description, which causes various issues with test discovery (and import order because test_utils is a package and not just a module, which causes additional problems for pytest) depending on exactly what path is used to run the tests. We worked around some of these in #128, but it would be best if this subpackage and the test_comms.py file it contains could be renamed with a different prefix like testing to avoid this conflict.