Change 3.1.2_dps.py section to be able to read JSON files from S3

[wildintellect]

TODO:

• Merge responses into single object
• Save the merged response to json (Modify the dps arg)
• Add --local True/False for accessing example data

[wildintellect]

I merged my code cell in 3.1.2 showing how to aggregate the response jsons (list of dictionaries) into a single json. Now we just need to port it over to the fetch https://github.com/lauraduncanson/icesat2_boreal/blob/master/notebooks/3.Gridded_product_development/3.1.2_GreenestPixelCompositing_python_NT-AM-PM.ipynb

Then the existing code 3.1.2 dps can be changed to load a single json to get it's bands, path to the json in S3 provided as an arg.

[nmt28]

ported over and tested