status 'aborted' instead of 'abort'

The [message spec](https://jupyter-client.readthedocs.io/en/latest/messaging.html#messages-on-the-shell-router-dealer-channel) has statuses `'ok'`, `'error'` and `'abort'`. However, messages which are aborted because they are in the queue when an execution results in an error with `stop_on_error` set get a reply with `status: 'aborted'`, instead of `'abort'`:

https://github.com/ipython/ipykernel/blob/35b1d1a823dd22a0fe4eb99e89463c2527a11271/ipykernel/kernelbase.py#L799-L810

We should probably just fix this, but since it affects any kernel based on Python, and apparently not many others use `status: 'abort'`, there's an argument for updating the message spec to match what the Python kernel has been doing.

There's also the issue that `'abort'` is deprecated in favour of using `'error'`, so maybe we should just change this code directly to use `'error'`.