Optimize DuckDB download process

[aguest-kc]

Description:

Updates the download logic for DuckDB to only create the download tables that are required for that specific download job. For example, if a Custom Account download only includes File A then we only need to create the File A download table in memory.

Technical Details:

Requirements for PR Merge:

1. Unit & integration tests updated
2. API documentation updated (examples listed below)
   1. API Contracts
   2. API UI
   3. Comments
3. Data validation completed (examples listed below)
   1. Does this work well with the current frontend? Or is the frontend aware of a needed change?
   2. Is performance impacted in the changes (e.g., API, pipeline, downloads, etc.)?
   3. Is the expected data returned with the expected format?
4. Appropriate Operations ticket(s) created
5. Jira Ticket(s)
   1. DEV-0

Explain N/A in above checklist: