Codechange: Extract code to build cargo acceptance string for re-use.

src/cargotype.h

@@ -214,6 +214,8 @@ void SetupCargoForClimate(LandscapeID l);
 bool IsDefaultCargo(CargoID cid);
 void BuildCargoLabelMap();
 
+std::optional<std::string> BuildCargoAcceptanceString(const CargoArray &acceptance, StringID label);
+
 inline CargoID GetCargoIDByLabel(CargoLabel label)
 {
 	auto found = CargoSpec::label_map.find(label);