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/float_struct.py

@@ -8,11 +8,10 @@ except ImportError:
     print("SKIP")
     raise SystemExit
 
-i = 1. + 1/2
+i = 1.0 + 1 / 2
 # TODO: it looks like '=' format modifier is not yet supported
 # for fmt in ('f', 'd', '>f', '>d', '<f', '<d', '=f', '=d'):
-for fmt in ('f', 'd', '>f', '>d', '<f', '<d'):
+for fmt in ("f", "d", ">f", ">d", "<f", "<d"):
     x = struct.pack(fmt, i)
     v = struct.unpack(fmt, x)[0]
-    print('%2s: %.17f - %s' % (fmt, v, (i == v) and 'passed' or 'failed'))
-
+    print("%2s: %.17f - %s" % (fmt, v, (i == v) and "passed" or "failed"))