shift+tab completion on chained methods

The behaviour in this issue has been raised previously in https://github.com/jupyterlab/jupyterlab/issues/12570 and https://github.com/altair-viz/altair/pull/2770#issuecomment-1364100231.

It seems it is not possible to make the docstring/function signature appear for chained methods using ipython/ipykernel.

See the following screencast:

As can be seen this can be reproduced with the following procedure:
Copy the following in a Jupyter notebook
```python
int().as_integer_ratio().count(
```
Press shift+tab to try to make the docstring/function signature appear.
Result, nothing happens.

When doing the same using a XPython Raw kernel (through `xeus-python`) the docstring/function signature does appear. See following screencast:

Reproduce the behavior in a Jupyter notebook with `int().as_integer_ratio().count(` and Shift+Tab, then compare it with the documented XPython Raw kernel behavior. Trace the ipython/ipykernel handling involved in showing docstrings or signatures for chained methods; done means the signature appears consistently for the reproduction case.

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