@Override
        protected SimpleConfigProducer<AnyConfigProducer> doBuild(DeployState deployState, TreeConfigProducer<AnyConfigProducer> parent,
                                                  Element producerSpec) {
            return new SimpleConfigProducer<>(parent, configId);
        }
The SimpleConfigProducer is the producer for elements such as container.
Must support overrides for that too, hence this builder

@author vegardh
config-model/src/main/java/com/yahoo/vespa/model/builder/xml/dom/VespaDomBuilder.java