Today, there are two different implementations of the DSS/CSS - one for the standalone/replica set case and the other for the shard case. This is prevents online promotions of RS to sharded clusters and also makes the Config shard behave differently based on whether it has the shard flag or not.

This ticket is to get rid of CollectionShardingStateFactoryStandalone entirely (perhaps only leave it for embedded) and use CollectionShardingStateFactoryShard.