mp_obj_print_helper: Handle a ctrl-c that comes in during printing

In #2689, hitting ctrl-c during the printing of an object with a lot of sub-objects could cause the screen to stop updating (without showing a KeyboardInterrupt).  This makes the printing of such objects acutally interruptable, and also correctly handles the KeyboardInterrupt:

```
>>> l = ["a" * 100] * 200
>>> l
['aaaaaaaaaaaaaaaaaaaaaa...aaaaaaaaaaa', Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyboardInterrupt:
>>>
```

0 files changed, 0 insertions, 0 deletions