Demonstrate use of GCS auth helpers

[raebot]

This PR demonstrates use of the new GCS auth helpers read_parquet, read_file, and geo_data_frame_to_parquet in a couple files. It removes the need to import gcsfs or google.auth packages and manage auth tokens. The idea here is to provide a few examples and then let analysts begin using these helper functions themselves as they find them useful. I also optimized imports in the files I edited while I was in there.

This PR relates to the helper introduced with this calitp-data-analysis PR.

Resolves #1547

[github-actions]

nbviewer URLs for impacted notebooks:

• ntd/sjcog_service_analysis/explore_sjcog_service.ipynb

[github-actions]

nbviewer URLs for impacted notebooks:

• ntd/sjcog_service_analysis/explore_sjcog_service.ipynb

[csuyat-dot]

Worked with Rae. Pulled latest commit of explore_sjcog_service.ipynb and was able to read in geojsons from GCS (w/ GCSGeoPandas) and ArcGIS (w/ geopandas). Entire notebook ran with no errors. Good to go.