Trucks should proactively avoid getting stuck from terraforming

1. Vehicles should avoid parking on tiles on, near, or surrounded by terraforming designations, especially designations on the same height level or above.
2. Before terraforming, the vehicle should check if doing so would block off access to the rest of the island.
These two AI changes are small but they should cause trucks to get stuck way less often, because most of the times I've had to recover a truck was from it parking in the middle of somewhere I was terraforming.
The second change could be something as relatively simple as "don't terraform a spot I just drove over five seconds ago", since that's likely the path the vehicle will take to get back to the rest of the island.