Export format for Editable Mappings/Proofreading annotations

[fm3]

Annotation download for proofreading annotations should include the infos to reconstruct the edited mapping. This essentially means the inserted and removed edges, this can be constructed from the update actions.

Should be flattened/compacted like this

def compact_update_actions(actions) -> Tuple[List[int, int], List[int, int]]:
  positive_set = {}
  negative_set = {}
  for action in actions:
    if action.is_positive:
      positive_set.add(action.edge)
      negative_set.remove(action.edge)
    else:
      positive_set.remove(action.edge)
      negative_set.add(action.edge)
  return list(positive_set), list(negative_set)

Should be encoded as zarr

Reupload should construct new update actions from this; create a new mergeable editable mapping annotation