media: Use glycin to load images

It is sandboxed so loading unknown media is safer. It also supports more formats than image-rs.

Fixes part of Images orientation metadata ignored when opened... (#1371 - closed) (images now open in the correct rotation, but we still generate thumbnails with the wrong rotation).
Fixes SVG not supported in media viewer (#1396 - closed).
Fixes Autoplay animated webp files (#1489 - closed).