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/string_format_modulo2_intbig.py

@@ -1,21 +1,23 @@
 # test formatting floats with large precision, that it doesn't overflow the buffer
 
+
 def test(num, num_str):
-    if num == float('inf') or num == 0.0 and num_str != '0.0':
+    if num == float("inf") or num == 0.0 and num_str != "0.0":
         # skip numbers that overflow or underflow the FP precision
         return
-    for kind in ('e', 'f', 'g'):
+    for kind in ("e", "f", "g"):
         # check precision either side of the size of the buffer (32 bytes)
         for prec in range(23, 36, 2):
-            fmt = '%.' + '%d' % prec + kind
+            fmt = "%." + "%d" % prec + kind
             s = fmt % num
             check = abs(float(s) - num)
             if num > 1:
                 check /= num
             if check > 1e-6:
-                print('FAIL', num_str, fmt, s, len(s), check)
+                print("FAIL", num_str, fmt, s, len(s), check)
+
 
 # check most powers of 10, making sure to include exponents with 3 digits
 for e in range(-101, 102):
     num = pow(10, e)
-    test(num, '1e%d' % e)
+    test(num, "1e%d" % e)