Update Indexer to Get all Documents via Athena

[rlingineni]

AWS Athena can quickly return S3 details.

The main problem is that in order to query, it requires creating a db-table for a schema. It's still cheap nonetheless.

To implement, we would need to dynamically update the Athena Table upon each new index config added or update and set up a config in the Cloudformation template accordingly.

It would be interesting to see how much of an improvement this might make. A good starting point before implementation is to do a study on a manual bucket with a bunch of documents, and replace the listObjects call with Athena.