protected void renderHit(Hit hit) throws IOException {
        if (!shouldRender(hit)) return;

        childrenArray();
        generator.writeStartObject();
        renderHitContents(hit);
        generator.writeEndObject();
    }
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