vehicles: rationalize damage on removal (CleverRaven#35444)

Fixes CleverRaven#23215

When removing vehicle parts, rationalize the damage to the damage
level * damage_scaling so that the removed parts will stack
nicely with each other.

src/vehicle_part.cpp

@@ -80,6 +80,9 @@ item vehicle_part::properties_to_item() const
         tmp.active = true;
     }
 
+    // force rationalization of damage values to the middle value of each damage level so
+    // that parts will stack nicely
+    tmp.set_damage( tmp.damage_level( 4 ) * itype::damage_scale );
     return tmp;
 }