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.
If micropython.native decorator doesn't compile, then we skill all
native/viper tests.
This patch also re-enables the ujson_loads test on NT.
Addresses issue #861, and partially addresses issue #856.
