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.
These tests involves testing allocation-free function calling, and in strict
stackless mode, it's not possible to make a function call with heap locked
(because function activation record aka frame is allocated on the heap).