* DEV: Implement uploads command entrypoint
- Setup Thor UploadsCommand for CLI
- First pass at modularizing various parts of the exising `uploads_import` script
* DEV: First attempt at modularizing missing uploads fixer task
Move missing upload fix to a dedicated uploads task implementation unit
* DEV: First attempt at modularizing missing uploads uploader task
Move uploader to a dedicated uploads task implementation unit
* DEV: First attempt at modularizing missing uploads optimizer task
Move optimizer to a dedicated uploads task implementation unit
* DEV: Various follow up fixes to get optimization working
- Start threads early
- Improve "log" message formatting
- Add missing `copy_to_tempfile` method on "uploader" task
* DEV: Refactor a bit more
Deduplicate and move most of threading premitives to base task as-is
* DEV: Remove redundant condition in uploads db migration
* DEV: More deduplication
Move task retry logic to base class and tidy up other implementation
details carried over from the existing script
