Debug: Add general mechanism to dump a sprite group chain

src/newgrf_engine.cpp

@@ -1635,3 +1635,17 @@ void AnalyseEngineCallbacks()
 		}
 	}
 }
+
+void DumpVehicleSpriteGroup(const Vehicle *v, std::function<void(const char *)> print)
+{
+	const SpriteGroup *root_spritegroup = nullptr;
+	if (v->IsGroundVehicle()) root_spritegroup = GetWagonOverrideSpriteSet(v->engine_type, v->cargo_type, v->GetGroundVehicleCache()->first_engine);
+
+	if (root_spritegroup == nullptr) {
+		const Engine *e = Engine::Get(v->engine_type);
+		CargoID cargo = v->cargo_type;
+		assert(cargo < lengthof(e->grf_prop.spritegroup));
+		root_spritegroup = e->grf_prop.spritegroup[cargo] != nullptr ? e->grf_prop.spritegroup[cargo] : e->grf_prop.spritegroup[CT_DEFAULT];
+	}
+	DumpSpriteGroup(root_spritegroup, std::move(print));
+}