Move queries into named directories

[fbertsch]

We will move each query into its appropriately named subdirectory, e.g. sql/search/search_clients_daily_v7.sql will move to sql/search/search_clients_daily_v7/query.sql.

The Airflow runner will have to be notified of this change as well.

Optional: Move view creation scripts to a view.sql file instead of query.sql.

We will also add a metadata.yaml file to every query subdirectory. There are currently only a few query writers so we should be able to appropriately fill-in owners, friendly_name, and description; optionally, some of the job descriptions can be put in labels, e.g. application, refresh, version, incremental.

For more details, see the public data proposal.