Add possibility to scan whole range of IPs at once

At this moment, ralph-cli can scan only single IP address at once. Although we can employ some bash scripts for scanning multiple hosts, it probably won't be very convenient and efficient. Therefore, we need to implement this functionality directly in ralph-cli.

(related issues: https://github.com/allegro/ralph/issues/2853, https://github.com/allegro/ralph/issues/2499)