This adds the Python files in the tests/ directory to be formatted with
./tools/codeformat.py. The basics/ subdirectory is excluded for now so we
aren't changing too much at once.
In a few places `# fmt: off`/`# fmt: on` was used where the code had
special formatting for readability or where the test was actually testing
the specific formatting.
The idea is that these tests can be run with just a test server running
on a test host, with device under test connecting to it, instead of
requiring Internet connection for testing.
Such setup is however WIP, and some tests in net_hosted/ are so far
written to connect to Internet, as there're not test server written
yet. This is expected to evolve over time.
