feat: Ability to apply a transformer to all events #3143

Description

Recently I started using bloc v8 and bloc_concurrency and I noticed that in this new version there is no way (or at least I couldn't find any way) to apply a transformer to all incoming events. Right now we can do something like this:

MyBloc(this.useCase) : super(const MyBlocState()) {
  on<Event1>(_event1);
  on<Event2>(_event2, transformer: debounced());
}

But what if we wanted to apply restartable transformer to all events?

Desired Solution

Ability to define global transformers.