feat: Bounding Box in provenance Files

[william-silversmith]

I was doing a downsample of an inference run, but I suspect that inference run covered only a small region of the dataset. If I knew the bounding box, I could restrict it somewhat. In Igneous, I found this is a good format:

      'bounds': [
        bounds.minpt.tolist(),
        bounds.maxpt.tolist()
      ],