instantiate modules if they have a default constructor

[ralph-bergmann]

Currently, the create method expects objects from all modules, even if they have a default constructor.

If a module has a default constructor, generate code to instantiate it, so the user does not have to.

old:

final coffee = await Coffee.create(DripCoffeeModule());

 static _i5.Future<_i1.Coffee> create(
      _i2.DripCoffeeModule dripCoffeeModule) async {
    // ...
  }

new:

final coffee = await Coffee.create();

  static _i5.Future<_i1.Coffee> create(
      {_i2.DripCoffeeModule dripCoffeeModule = _i2.DripCoffeeModule()}) async {
    // ...
  }