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/micropython/heapalloc_traceback.py

@@ -2,6 +2,7 @@
 
 import micropython
 import sys
+
 try:
     import uio
 except ImportError:
@@ -15,6 +16,7 @@ try:
 except:
     pass
 
+
 def test():
     micropython.heap_lock()
     global global_exc
@@ -22,9 +24,10 @@ def test():
     try:
         raise global_exc
     except StopIteration:
-        print('StopIteration')
+        print("StopIteration")
     micropython.heap_unlock()
 
+
 # call test() with heap allocation disabled
 test()