Auto upload: Make it so that individual upload jobs can be dynamically changed or stopped without having to force stop the app

I noticed that when I try to change the remote folder or even re-disable the local folder, the current upload job continues to run as it did before, and those changes don't seem to take effect until that current upload job. If file uploads were treated on a per-file basis rather than a per-folder or per-job basis, then any settings to auto uploads for a local folder could change for the next file instead of waiting for the entire job to finish.

This issue is related to #16550.

Start by reading related issue #16550, then trace the auto-upload job lifecycle described here. Define how remote-folder changes, local-folder disabling, and stopping a job should affect the next file without force-stopping the app; done means these changes take effect while the job is running.

Written by the indexing model from the issue text.