Refactored debian packaging

• Increased debian compatibility level to 11
• Use pybuild as the debian build system
• Updated build and package dependencies
• Switched from init script to systemd service
• Install README to the debian package docs
• Removed no longer used pycompat and pyversions debian files
• Removed no longer used openxcap.dirs and openxcap.install debian files
• Install the configuration sample and extra data files from setup.py