[ListMonitor] [numberOfObjects()] Calculate the number of objects in all sections by summing the number of objects stored in `NSFetchedResultsSectionInfo`.
[ListMonitor] [numberOfObjects()] Calculate the number of objects in all sections by summing the number of objects stored in `NSFetchedResultsSectionInfo`.

There is a performance problem in Swift when calling `count` method on an array with a large number of fetched objects. It requires casting the array between Objective-C and Swift, that is pretty slow.

JohnEstropia/CoreStore,ruslanskorb/CoreStore,ruslanskorb/CoreStore,JohnEstropia/CoreStore