Exclude private datasets from 6 geoportal datasets, GTFS digest

[tiffanychu90]

• Add a function in gtfs_utils_v2 to grab either a list or the df of public datasets - normally, this is preferred because we get a list of schedule_gtfs_dataset_keys we can keep.
  • Add function to filter df down in publish_utils -- sometimes in GTFS digest, we do not have schedule_gtfs_dataset_key, so we use schedule_gtfs_dataset_name to filter.
• high quality transit areas and open data - do this in last steps before exporting
• speeds - do this in publish_open_data via parquet filtering and publish_public_gcs
• GTFS digest - do this in merge_* scripts so that all the dates are concatenated, and before exporting, private datasets are dropped. This should allow the portfolio yaml to build and report to run as usual.
• Run Sep monthly publishing and double check results are as expected (exclude Big Blue Bus Swiftly Schedule)
• Research Request - Suppress private datasets from being published  #1220

TODO related GTFS Digest:
some redundancies were noticed while updating merge scripts. wherever references are shared, adapted functions to take additional uses.

• this affects service hours, having weekday / weekend columns in addition to rows holding those values is confusing, since column values are mixing normalized (per day) and not normalized (sums). also month changed to month_year because month typically holds month values (1-12 or Jan-Dec).
• need to rerun all the merge_* scripts to create new concatenated digest tables