Reverse geocode 'unknown' flight log locations to show 'nearby' place references

In concept, it would add the following as a 'location' reference when Airport or Custom codes were not found:

If geo.locality within threshold → use “<d> <bearing> of <locality>”

Else if geo.route within 2 km → “near <route>

These would be used in all the same places (Flying timeline, History, Flight Explorer and Notifications)