dns/{ldns,py-ldns}: Update 1.9.0 => 1.9.2
While here, introduce SOVERSION variable for easy update.
Release Notes:
- https://community.nlnetlabs.nl/t/ldns-1-9-1-released/3403
- https://community.nlnetlabs.nl/t/ldns-1-9-2-released/3404
Changelog:
https://github.com/NLnetLabs/ldns/blob/1.9.2/Changelog
PR: 296232
Approved by: osa, vvd (Mentors, implicit)
MFH: 2026Q2
(cherry picked from commit 29b9a35715f663d7e8735bfeebf3226e7046fe7b)