Restore Sphinx manpage reference rendering with Docutils 0.22

[Mirochill]

Summary

• restore Sphinx's custom manpage reference renderer after Docutils 0.22 installs an instance-level visit_reference
• preserve the historical reference styling tuple when newer Docutils versions no longer expose it
• add a regression test for :ref: and :doc: rendering in man pages

Root cause

Docutils 0.22 assigns visit_reference on the manpage translator instance according to its text_references setting. That shadows ManualPageTranslator's specialized Sphinx implementation, so internal references render as raw <uri> fragments such as <#other-ref> and <> instead of styled text.

Fixes #14427.

Validation

• Not run locally
• relying on the repository's GitHub Actions / Read the Docs checks for remote validation