protected void renderAllFields(Hit hit) throws IOException {
        fieldConsumer.startHitFields();
        renderTotalHitCount(hit);
        renderStandardFields(hit);
        fieldConsumer.endHitFields();
    }
Creates a json renderer using a custom executor.
Using a custom executor is useful for tests to avoid creating new threads for each renderer registry.
container-search/src/main/java/com/yahoo/search/rendering/JsonRenderer.java