Validate wrong filebeat config combinations

[ruflin]

• Check ignore_older and close_older
• Check close_removed and clean_removed combination
  • This will be indirectly solved by Only cleanup state if harvester finished #2075 as states can only be removed if reading is finished.
• Check clean_idle > ignore_older + scan_frequency

[ruflin]

@urso I have some implementation issue here I was hoping perhaps you could help. close_removed is part of the harvester config and the prospector does not know about it. clean_removed is part of the prospector config and the harvester does not know about it. The problem is now how to verify that both are set. It would be easy to just add close_removed also to the prospector config just for the validation. At the same time I think it is really nice that we have the two separated and would like to keep it this way. Any alternative idea?