doc: Fix gen-manpages, rewrite in Python

Rewrite the manual page generation script in Python.

This:
- Solves '-' stripping issue (fixes #22681)
- Makes that copyright footer is generated again

doc/release-process.md

@@ -6,7 +6,7 @@ Release Process
 ### Before every release candidate
 
 * Update translations see [translation_process.md](https://github.com/bitcoin/bitcoin/blob/master/doc/translation_process.md#synchronising-translations).
-* Update manpages, see [gen-manpages.sh](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/README.md#gen-manpagessh).
+* Update manpages, see [gen-manpages.py](https://github.com/bitcoin/bitcoin/blob/master/contrib/devtools/README.md#gen-manpagespy).
 * Update release candidate version in `configure.ac` (`CLIENT_VERSION_RC`).
 
 ### Before every major and minor release