Add duplicate filter score weight for lower filesize in pixel-for-pixel duplicates

[roachcord3]

Right now we have weights for higher quality, higher resolution, higher filesize, more tags, and earlier import time.

But when it comes to pixel-for-pixel dupes, the first two don't matter at all, and when it comes to filesize, you ~~pretty much always~~ might want the smaller file, not the larger one (to deal with stuff like poorly compressed pngs.)

Please add a weight for lower filesize in pixel-for-pixel duplicates, even trivially lower filesize. And please make sure the higher filesize weight does not apply.

Related: #745 since it would help highlight the size difference in the UI.

edit: after lots of time spent with negative values in the weights since that feature was added, I've begun to find that the smaller file isn't necessarily better, but regardless, I do think having a separate set of weights for pixel-for-pixel dupes compared to other dupes would be beneficial. Most of the time, a significantly larger pixel-for-pixel dupe is inferior, but not so if they are not pixel-for-pixel dupes, especially when comparing JPEGs. Trivially larger pixel-for-pixel dupes are (in my current, not past, opinion) usually superior, on the other hand, whereas it's a toss-up with non-pixel-for-pixel dupes (again, comparing JPEGs, I've found that a trivially larger one might have worse-looking compression anyway.)