resolves #3912

When creating a dataset example from a span, the annotations associated with that span will be "snapshotted" and included in the span metadata under a new key: annotations. This key will always be present and empty if the span has no annotations.

If the span does have annotations, the structure of the annotations will be a mapping:

metadata:
  annotations:
    annotation_name:
      label: label
      score: score
      explanation: explanation
      metadata: metadata
      annotator_kind: kind