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();
            }
        }

首先检查 #130 中的工作，并定位 SmoSortedList 对 SortedList 的使用。跟踪其枚举器当前如何公开值，然后验证泛型实现是否可以直接返回列表的 Values，而无需嵌套的枚举器代码。