During FCV upgrade/downgrade, routing information and even the metadata collections can contain a mix of shardIds and shardUUIDs. We need to evaluate all aggregations which use shardIds to see if they need to be updated to work via either reference.

This is the first ticket in this stream of work and is responsible for evaluating the usages of getDatabaseForShard to see if it needs to be updated to handle mixed scenarios and (if so) update it to do so.