pydantic model docs, objects.inv, aftermath removing qcel autodoc

[loriab]

Description

Changelog description

• [x] remove use of qcel autodoc and __base_doc__ in qcf code that were removed in MolSSI/QCElemental#289
• [x] add use of https://github.com/mansenfranzen/autodoc_pydantic by replacing .. autoclass:: with .. autopydantic_model:: . hopefully I didn't miss any.
• [x] for qcportal docs, I added FractalClient so the class would appear in objects.inv. I removed Mol so that qcelemental.models.Molecule didn't appear in objects.inv. there's still a couple qcel refs in there, but they're to Protocols that aren't acutally exported by qcel, and I didn't want to change code.
• [x] updated sphinx autodoc options, updated intersphinx, effectively switched main build to rtd.
• [ ] I can't see how the docs build is going to go, but both qcportal and qcfractal docs builds work fine for me locally. here's a GHA docs build snippet (https://github.com/MolSSI/QCElemental/blob/master/.github/workflows/CI.yml#L81) but I don't want to be radically switching from rtd to gha on master, and I see your gha's in next are much different.
• [ ] CI errors
  • ConnectionRefusedError to the molssi api server?
  • KeyError: "Collection 'Dataset:ds_gradient' not found."

Status

• [x] Code base linted
• [x] Ready to go

[codecov[bot]]

Codecov Report

Merging #716 (528ee57) into master (ceff64f) will decrease coverage by 11.08%. The diff coverage is 100.00%.

[bennybp]

No longer applicable now that docs have been refactored :)