Add the ReadOnlyCollectionPage<T> base class as a common API for paginated collections
Update IQueueingService to use ReadOnlyCollectionPage
Update IDatabaseService to use ReadOnlyCollectionPage
Update IDnsService to use ReadOnlyCollectionPage
Update ILoadBalancerService to use ReadOnlyCollectionPage
Update IMonitoringService to use ReadOnlyCollectionPage
Consistently use ReadOnlyCollection<T> as the return value for non-paginated collections