Currently, the CatalogCache returns an intermediate "combo" object called CachedCollectionRoutingInfo for its collection routing methods. We should go in a direction where the ChunkManager is the only thing used for routing, so we should make the CatalogCache return it directly instead.

As a follow-up step, we should remove all places which differentiate between sharded and unsharded collections and push that logic in the ChunkManager's routing methods. That way when we make all collections be sharding-aware, we will only have to make changes there.