Issue #3625521: Answer media image structures on a field that is not media

The media image and video structures called media methods on whatever the field referenced, which fataled on a site that keeps a picture in an image field under the same name. An image field is now answered with the same structure as a media image, a file field with the URL of its video, and any other reference is skipped. The field kind is read off the field the field map resolves to, and the single media image reads that field too. The video block of a paragraph reads the duration off whichever file there is.

Closes #3625521