fix: do not merge awareness sync data info client update sync data

[LucasXu0]

  fn receive_local_state(
    &self,
    origin: &CollabOrigin,
    object_id: &str,
    _event: &Event,
    update: &AwarenessUpdate,
  ) {
    let payload = Message::Awareness(update.encode_v1()).encode_v1();
    // ...
      ClientCollabMessage::new_update_sync(update_sync) <- Here

In the previous implementation, the awareness data was associated with the ClientCollabMessage::new_update_sync, which caused the awareness update to be merged into the client update.

[LucasXu0]

When merging the last and next, we should check if the next is mergeable. If the last is mergeable but the next is NOT, they should not be merged.

[LucasXu0]

@Horusiath could you please confirm whether it was a typo or intentional to set the awareness update as update_sync instead of awareness_sync?