Codechange: Use C++ features for train wagon overrides. (#9141)

This removes the need for C-style array management and allows use of iterators to perform wagon override lookups.

src/engine.cpp

@@ -66,12 +66,6 @@ static_assert(lengthof(_orig_rail_vehicle_info) + lengthof(_orig_road_vehicle_in
 
 const uint EngineOverrideManager::NUM_DEFAULT_ENGINES = _engine_counts[VEH_TRAIN] + _engine_counts[VEH_ROAD] + _engine_counts[VEH_SHIP] + _engine_counts[VEH_AIRCRAFT];
 
-Engine::Engine() :
-	overrides_count(0),
-	overrides(nullptr)
-{
-}
-
 Engine::Engine(VehicleType type, EngineID base)
 {
 	this->type = type;
@@ -136,11 +130,6 @@ Engine::Engine(VehicleType type, EngineID base)
 	}
 }
 
-Engine::~Engine()
-{
-	UnloadWagonOverrides(this);
-}
-
 /**
  * Checks whether the engine is a valid (non-articulated part of an) engine.
  * @return true if enabled