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/math_fun_bool.py

@@ -6,8 +6,7 @@ except ImportError:
     print("SKIP")
     raise SystemExit
 
-test_values = [1, 0, -1, 1.0, 0.0, -1.0, float('NaN'), float('Inf'), 
-               -float('NaN'), -float('Inf')]
+test_values = [1, 0, -1, 1.0, 0.0, -1.0, float("NaN"), float("Inf"), -float("NaN"), -float("Inf")]
 
 functions = [isfinite, isnan, isinf]