Correct documentation and use of type hints

[erikwrede]

We should upgrade graphene to use modern type hints. In that process, type hints should be removed from the class/method documentation to have the code as the single source of truth for typing.
We can use https://github.com/tox-dev/sphinx-autodoc-typehints to automatically add type hints back into the docs.

PRs addressing this issue should at least fix the entire file they are contributing to reduce double-checking effort and streamline the process.

Known issues:
#1100 , see #1282 (Query on schema)

[anentropic]

This would big a big help to anyone wanting to use graphene in a typed codebase

Because the 3rd party type defs we've been using seem to be abandonware (e.g. trialspark/graphene-stubs#27 and no commits for ~3 years)