perf(nextup): batch the user data reads the next episode selection makes

Next Up walked every series in an unpaginated loop and read user data one
episode at a time, so the Home screen row cost two queries per series once the
cache was gone.

- read the played state of every candidate episode in one query
- read the versions the resume check and the last played date need in one query each
- default PrefetchedUserData on IUserBaseItemComparer so plugin comparers still compile
- cover the bounded query count and the plugin comparer with tests
- share one database across the replica tests

MediaBrowser.Controller/Sorting/IUserBaseItemComparer.cs

@@ -33,8 +33,13 @@ namespace MediaBrowser.Controller.Sorting
 
         /// <summary>
         /// Gets or sets user data for the items being sorted, keyed by item id, read once up front.
+        /// A comparer that does not store it reads its user data one item at a time instead.
         /// </summary>
         /// <value>The prefetched user data, or <c>null</c> when none was prefetched.</value>
-        IReadOnlyDictionary<Guid, UserItemData> PrefetchedUserData { get; set; }
+        IReadOnlyDictionary<Guid, UserItemData> PrefetchedUserData
+        {
+            get => null;
+            set { }
+        }
     }
 }