Define a checklist of upgrade steps

[LukeShortCloud]

1. Fix the Pacman configuration file (for example, the [community] repository no longer exists)
2. Update Pacman mirrors (with reflector on Arch Linux or pacman-mirrors on Manjaro)
3. Update Pacman repository cache and rebuild the database (pacman -S -y -y)
4. Update archlinux-keyring (and manjaro-keyring on Manjaro)
5. Fix various package breakages (for example, renamed Java packages)
6. Update all packages (pacman -S -u)