Completion in python mode + IPython

[Ergus]

Hi all:

Recently I have been using python mode and I noticed that the
completions in the python shells are too basic.

For interactive shells IPython offers a more friendly completion set and
it used to work in the past with emacs just with

```
python-shell-interpreter "ipython"
python-shell-interpreter-args "--simple-prompt"
```

I found that the issue is that the default value:

python-shell-completion-native-enable t

Uses only the basic readline completions, while Ipython uses a different
very improved api.

The commit 0b9c7148fd681c8ad63fd0eb3895d from Liu Hui (Jan 28, 2024)

Solves this issue for the `python-shell-completion-setup-code` (the
non-default one).

As python-mode is supposed to support ipython, why we don't include the
same in `python-shell-completion-native-setup`.

 Is this intended?

Best,
Ergus