POC: Ability to cancel the upload of attachments in app

## Is your feature request related to a problem? Please describe
When uploading files, it is impossible to cancel the upload before the process is finished. There is only a "Delete attachment" button that gets a 404. It is frustrating as a user to be forced to wait before canceling/deleting.

## Describe the solution you'd like
When uploading a file, have a button there for canceling the upload. Replacing the "delete attachment" button until it is finished. Something like this:

## Describe alternatives you've considered
None

## Additional context
Nasjonalbiblioteket expect some users to deal with large files, where this would improve the user experience.

No specific file or test is named. Start at the attachment upload entry point in the React app and trace how the upload and delete controls change during an in-progress upload; done means users can cancel an active upload and the existing delete action is available once it finishes.

Written by the indexing model from the issue text.