tox.ini: Add opensuse, add/update opensuse.txt across build/pkgs/ #30619
Description
To test openSUSE Leap:
tox -e docker-opensuse-standard
Depends on #30663
Depends on #30900
Depends on #30899
CC: @kliem @dimpase @jhpalmieri @seblabbe
Component: packages: standard
Author: Jan Engelhardt, Matthias Koeppe
Branch/Commit: e5d114b
Reviewer: Matthias Koeppe, Jonathan Kliem, Dima Pasechnik
Issue created by migration from https://trac.sagemath.org/ticket/30619