Allow harvester to remove overgrown crops

[PatrikLundell]

Summary

None

Purpose of change

Partiall address #83161 by allowing harvesters to remove overgrown crops, while still not dealing with harvestable and overgrown crops not being traversible by vehicles.

Describe the solution

Modify the harvesting code to process overgrown crops as well, to clear the tile but producing no yields.

Describe alternatives you've considered

Deal with the steel plants as well. The harvester vehicle in the game is not compatible with the fields in the game when steel plants are around:

• Fields are planted with double rows, while harvesters process 3 single rows at a time.
• Fields are planted in a real world fashion with curving rows. Game vehicles can't move like that.
  This means game harvesters will crash into game crops on fields and gradually get destroyed unless they're rebuilt by the player before use.

Harvest straw or withered plants as some kind of generic result instead of nothing.

Testing

Teleported to overgrown field, debug spawned a reaper tractor, engaged the reaper, and tried to reap the overgrown crops at the edge of the field (so the vehicle wouldn't smash into any crops). Verified nothing happens to the crops.
Modified the code.
Repeated the above and saw the overgrown crops disappeared, with nothing harvested.

Additional context