upgrade script for 5.0

This MR changes the packaging files to do the following:

• before package uninstallation, systemd socket configuration is listed and saved
• after package installation, a lua script is executed to generate net.listen() commands from the saved configuration
• the generated commands are saved in /var/lib/knot-resolver/.upgrade-4-to-5/kresd.conf.net and printed out during interactive package upgrade

TODO: ensure package upgrade passes:

• Arch
• Debian
• Ubuntu
• CentOS
• Fedora
• Leap

Related #485 (closed)