"PigRelBuilder#create" maybe a wrong place to set Hook.REL_BUILDER_SIMPLIFY

[JiaTao Tao]

Hi, in PigRelBuilder#create, we set Hook.REL_BUILDER_SIMPLIFY to false:

  public static PigRelBuilder create(FrameworkConfig config) {
    final RelBuilder relBuilder = RelBuilder.create(config);
    Hook.REL_BUILDER_SIMPLIFY.addThread(Hook.propertyJ(false));
    return new PigRelBuilder(
        transform(config.getContext(), c -> c.withBloat(-1)),
        relBuilder.getCluster(),
        relBuilder.getRelOptSchema());
  }

I have two doubts:
1. Why we set FALSE here cuz its default value is true;
2. This maybe not the suitable place to set  "Hook.REL_BUILDER_SIMPLIFY",
IMO we should use this in user code, not in the frame code, cuz once we
done this in frame code, we can not change this config anymore.

Regards!

Aron Tao