Initial filtering on Belum Selesai checkout status

It's essentially the same as filtering for existing checkouts, except we'll:
+ Add Pilot/Airstrip pairs for which no checkouts exists
+ Convert 'Belum' to 'Unprecedented' if no Pilot is checked out for that combo
+ Remove Pilot/Airstrip pairs for which all AircraftTypes are Sudah Selesai
Test cases for Belum Selesai checkout filtering
Integrating Belum Selesai checkout filtering
Clarifying the intent of the test