Enable showing typehints in sphinx function/method signature and content

[aucampia]

Enable showing typehints in sphinx function/method signature and content

With current config sphinx only adds type hints to method/function
signatures.

This patch changes the autodoc_typehints from the default of
signature to both, which is described by sphinx documentation as:
"Show typehints in the signature and as content of the function or method".

For more info see:
https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#confval-autodoc_typehints

Other changes:

• Harmonize sphinx version restriction across different places where
  dependencies are defined.
• Sort requirements files.

[aucampia]

I compared various options for type hints and sphinx, they can be compared against docs generated current master as of writing this:

sphinx-autodoc-annotation

https://aucampia.github.io/pages-raw/Aenei9iu/rdflib.sphinx_autodoc_annotation/apidocs/rdflib.html#rdflib.term.bind

sphinx-autodoc-typehints

https://aucampia.github.io/pages-raw/Aenei9iu/rdflib.sphinx_autodoc_typehints/apidocs/rdflib.html#rdflib.term.bind

autodoc_typehints="both"

https://aucampia.github.io/pages-raw/Aenei9iu/rdflib.sphinx_adthb/apidocs/rdflib.html#rdflib.term.bind

Conclusion

To me the best option seems to be autodoc_typehints="both", as this retains the annotations in the signatures and adds them in the documentation body, integrating them with other docstrings.

sphinx-autodoc-annotation seems to not use some types, and also the type docs it makes are not hyperlinked.

sphinx-autodoc-typehints has somewhat better output than autodoc_typehints="both" in some select situations, but there is no way to retain the types in signatures.

Feedback welcome though.