Rework Doc API Reference

[FedericoNegri]

During the technical review, the api reference section in the doc has been reworked to use sphinx-autoapi.
The resulting doc doesn't look great to me. Main issues:

1. The auto generated api includes subpackages/modules that are of little use for the users. These for instances
   
2. Doc of pydantic models doesn't look nice, example:
   
   vs using autodoc_pydantic
   
3. Sphinx produces tons of GL08 warnings about missing docstrings of pydantic models. Sources also still contain the old rst files for api doc, which are unused by now.

I'd prefer going back to the previous approach of a more handcrafted api reference, only including what really makes sense for a user to browse in a doc. Otherwise, they're just better off opening the sources.

Something I liked more of the autoapi one is the summary tables, so I'm using more of autosummary to get these tables

Link to latest html artifact

@RobPasMue @klmcadams what do you think?

[RobPasMue]

Looks good for me @FedericoNegri - we just wanted to reduce the maintainability of the docs by using sphinx-autoapi since it generates automatically everything for you and your API docs never go out of sync due to missing documented classes, methods etc. If you prefer this approach, by all means, go for it :)