Replace SmoSortedList usage of SortedList with SortedList<ObjectKeyBase, T>

After completing #130, push the type parameters further down into the implementation so we can remove code like this and just return the Values from the list.

        // nested enumerator class
        // we need that to override the behaviour of SortedList
        // that exposes an IDictionaryEnumerator interface
        internal sealed class SmoSortedListEnumerator : IEnumerator 
        {
            private IEnumerator baseEnumerator;
            
            internal SmoSortedListEnumerator(IEnumerator enumerator) 
            {
                this.baseEnumerator = enumerator;
            }

            public object Current 
            {
                get 
                {
                    return ((DictionaryEntry)baseEnumerator.Current).Value;
                }
            }

            public bool MoveNext() 
            {
                return baseEnumerator.MoveNext();
            }
            
            public void Reset() 
            {
                baseEnumerator.Reset();
            }
        }

Start by reviewing the work in #130 and locating SmoSortedList's use of SortedList. Trace how its enumerator currently exposes values, then verify that the generic implementation can return the list's Values directly without the nested enumerator code.