superbuild: support older Python versions
- Ben Boeckel: older-python-testing (common-superbuild!627 (merged))
- Ben Boeckel: setuptools-older-python-support (common-superbuild!624 (merged))
- Mathieu Westphal: fix_qt5_compilation_xcb (common-superbuild!628 (merged))
- Ryan Krattiger: ci_annotations (common-superbuild!625 (merged))
Backport: release