We can find throughout the code several instances where we check whether the collection is sharded in order to take a decision, now that we're setting the groundwork for PM-3338, we should change the API to hide some details about the collection, so there are no wrong assumptions about data placement.

We could for the pointed case, for example, expose documentBelongsToMe directly inside the ChunkManager but internally making it a no-op for non splitable collections, considering, there won't be any need to filter results from an unsplittable collection.

The purpose of this ticket is to remove the isSharded function from the collection description and properly handle the places where the function is called.