Ensure All Collection Extensions Has Consistant DoesNotHaveItems Methods

[RealDotNetDave]

Make sure that all the collection extensions has a DoesNotHaveItems method. Example:

public static bool DoesNotHaveItems<T>(this ObservableCollection<T> list) => list?.Count <= 0;

1. ArrayExtensions
2. ListExtensions
3. ReadOnlyCollectionExtensions
4. SortedDictionaryExtensions
5. SortedSetExtensions