Using prediction with previously selected output folder

If we run prediction from on-screen images with an output folder that we have previously used for prediction, all predicted images from previous predictions show up in the napari viewer.

This is because after prediction, we look in the target folder and load all images from it.

I think there's two ways around this:
If the user has selected an output folder which already has predictions saved to it, warn them that we will delete these if they choose to continue or to select alternate folder for outputs. Users cannot save prediction results into the same output folder unless they choose to delete the existing prediction results)

Have cyto-dl create a sub folder, numbered for each prediction run, and only load images from the most recent prediction run. (Users can save multiple times into the same output folder, and we can recognize the most recent prediction run and only show those images)