If tasks are not submitted for processing, then the imagery is never saved in the correct S3 path

[spwoodcock]

• I upload some imagery.
• I don't want to process any of the tasks, as they all have partial imagery or need parts reflown.
• I click to 'Finish' without processing any tasks.
• The imagery remains in user-uploads, and is never moved under the correct path {task_id}/images/.
• The logic to do this is in process_batch_images, but should be decoupled from the processing, also being triggered when the user decided to 'Finish' but not process yet.
• If they want to process the task in future, we should also move additional imagery added under user-uploads to {task_id}/images/, then submit all the images for the task together.

[linear]

TECH-952