Product Images: Bulk Upload Shows Every File You Selected

Bulk uploading product images was sometimes finishing with fewer thumbnails than the number of files you had selected — a record was created for each one, but a couple of tiles never rendered. Files being uploaded in the same batch are now given unique upload names, so two files that happen to share a filename no longer collide on upload, and the file key that we save on each image matches the actual location the file was written to so its thumbnail resolves.