Add ancestor_ids to prediction results (iOS)

[albullington]

Currently, Android is returning an array of ancestor_ids in prediction results, as shown below. We should also include these in the iOS prediction results.

Ancestor ids are necessary to make the AR camera work offline, since they're required to save an observation in Realm (both for figuring out the iconic taxon id and for giving Our Planet challenge credit).

[alexshepard]

this only happens in response to takePictureAsync, right? not in the onTaxaDetected callback?

[albullington]

On Android it's also in the onTaxaDetectedcallback, but all the offline parts of Seek will work as long as ancestor_ids is in the takePictureAsync prediction.

[albullington]

We likely still want to have parity in the way iOS and Android return results at some point. Closing this for now since I'm able to use the full list of returned predictions to create an ancestor_ids list within React Native (and get iOS working offline).