[CI] Adapt test version following target computers OS updates and new features

- change QA checks and Package building to use 3.11 = official version
- change second (required) test version from 3.10 to 3.12 to match mFLES update
- make pages depend on success of 2nd required version
- change third (optional) test version from 3.8 to 3.10 to match dev laptop update
- deprecate 3.8 support as new dump file cmd of the ConfServ requires at least Python 3.9 (= optional 4th test)