[Feature Request] Filter by string in the whole exif metadata

[Trevor-Z]

Images generated on Civitai don't tag the name and hash of their models in the exif in a way that's recognizable to DiffusionToolkit. So it's not possible to filter those images by model. Other generators might have the same problem.

To solve this issue and others of the same sort, I'd like to suggest an option to filter images by a text string anywhere in the metadata, without regard for field or category.