refactor: Change Producer Interface to generalize initialization

[vmarchese]

The current interface is:

type Producer interface {
	Produce(k []byte, v []byte, o any)
	io.Closer
}

and it does not define an Initialize method.
However, every createXXX method in the emitter.go file, initializes the producer from a configuration file.

The Initialization should be independent from the configuration file but should initialize the Producer with a default Constructor (e.g.: producer.New(...) (Producer, error)
The actual configuration should be hidden in the Factory.