Backport helpers for hyperlinks in manual pages [v9_16]

Replacement for backport of MR !5934 (merged)

We have decided not to backport all the hyperlinking to v9_16 branch. This MR adds Sphinx roles and directives available in the main branch, but these do almost nothing. It is meant as compatibility shim to simplify doc backports.

Sphinx built-in :option: is now overridden to act and render as `` literal syntax to avoid problems with undefined :option:targets.