[System.IO.KeventWatcher] More fixes and MS behavior matching for the new implementation.
* Fixed the FileSystemEventArgs.Name property for all events
* Fixed regression of bug #5747 (and related path normalizing issues) https://bugzilla.xamarin.com/show_bug.cgi?id=5747
* Improved error handling, set hard limit on file descriptors to 200 for now to help isolate issues
* Fixed issues with rapid event Changed+Renamed firing