BridgeJS: Fix closures with struct return

[wfltaylor]

Currently, the following code will result in generated code that fails to compile.

@JS public struct Animal {
    public let type: String
}

@JS func roundtripAnimal(_ animalClosure: (Animal) -> Animal) -> (Animal) -> Animal

The generated code uses bridgeJSLiftReturn with no arguments, which doesn’t exist.

This fixes this by adding an overload for bridgeJSLiftReturn which uses the stack ABI.