fix: Prepares for IPooledEnumerable removal (#1548)

### Summary

- Removes `IPooledEnumerable` (non-generic)
- Changes `IPooledEnumerable<T>` so that  `Free()` is replaced with the `IDisposable` pattern

Projects/UOContent/Items/Misc/Firebomb.cs

@@ -132,7 +132,6 @@ public partial class Firebomb : Item
                                 targets.Enqueue(m);
                             }
                         }
-                        eable.Free();
 
                         while (targets.Count > 0)
                         {

Projects/UOContent/Items/Misc/MorphItem.cs

@@ -88,8 +88,6 @@ public partial class MorphItem : Item
             }
         }
 
-        eable.Free();
-
         ItemID = found ? _activeItemId : _inactiveItemId;
 
         Visible = ItemID != 0x1;

Projects/UOContent/Items/Misc/OilFlask.cs

@@ -60,8 +60,6 @@ public partial class OilFlask : Item
                     }
                 }
 
-                eable.Free();
-
                 if (!didStack)
                 {
                     emptyFlask.MoveToWorld(Location, Map);