DOC: use sphinx autoapi instead of autosummary

### Description of the modifications

Pyansys project are switching from sphinx extension `autosummary` to `autoapi`.
This should probably wait a bit as we might need some changes associated to https://github.com/readthedocs/sphinx-autoapi/pull/399. Since this PR is taking quiet some time to be merged, the project might be forked by pyansys and we should point to that version in that case.

*Note*: changing the extensions should solve the issue we are having when building pdf (using `sphinx-build -M latex` with `numpydoc` and `autosummary`). Currently we aren't able to remove the warnings that are triggered on the Enum classes.

### Useful links and references

https://github.com/ansys/pyedb-core/pull/354#issuecomment-1904389263

Start with the Sphinx configuration and the current autosummary and numpydoc extensions. Check the status of sphinx-autoapi pull request 399 and whether the PyAnsys fork is required, then run `sphinx-build -M latex` to compare the Enum warnings. Done means the project builds its PDF documentation with autoapi and the reported warnings are resolved.

Written by the indexing model from the issue text.