DCP system events should be considered encapsulated within OSO snapshots

The Collections spec states:

During receipt of the OSO snapshot (i.e. begin received, but not the end) keep track of the greatest seqno received, consider this X.
X = max(X, received message.seqno).
The client must do this tracking for all DCP mutation, deletion, expiration and system events. If the client enabled synchronous replication, they would also need to include DCP prepare and abort messages.

Analytics DCP client does not consider system events to be within the OSO snapshot tracking, this should be fixed in Neo.