tests: Format all Python code with black, except tests in basics subdir.

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.

tests/float/array_construct.py

@@ -9,5 +9,5 @@ except ImportError:
         print("SKIP")
         raise SystemExit
 
-print(array('f', array('h', [1, 2])))
-print(array('d', array('f', [1, 2])))
+print(array("f", array("h", [1, 2])))
+print(array("d", array("f", [1, 2])))