Use `autodoc-process-bases` to substitute TypeVars for their bounds in base classes in docs

### What's the new feature?

Use `autodoc-process-bases` to substitute TypeVars for their bounds in base classes in docs. This is similar to the existing function to do it in function annotations.

See `documentation/source/conf.py` and https://www.sphinx-doc.org/en/master/usage/extensions/autodoc.html#event-autodoc-process-bases.

### What value does this add?

Show inheritance with Intersphinx links without needing to include TypeVars in the compiled documentation. Currently these links are broken.

### Is there an alternative you've considered?

_No response_

### Additional context

_No response_

Start with documentation/source/conf.py and the Sphinx autodoc-process-bases event documentation. Check the existing function-annotation TypeVar substitution and the open pull request for the current approach. Done means generated inheritance documentation substitutes TypeVars for their bounds and the affected Intersphinx links work.

Written by the indexing model from the issue text.