fix: Changes Map.Sector.Items to link list. (#1547)

### Summary

Eliminates `IPooledEnumerable<T>` and `eable.Free()` from `Map` for items. This drastically simplifies code that iterates in range, for example:

```cs
foreach (var item in m.GetItemsInRange(5))
{
}
```
The code above no longer requires an eable and calling `Free()`.

Projects/UOContent/Engines/Doom/LeverPuzzle/LeverPuzzleController.cs

@@ -197,9 +197,7 @@ public partial class LeverPuzzleController : Item
     [Usage("GenLeverPuzzle"), Description("Generates lamp room and lever puzzle in doom.")]
     public static void GenLampPuzzle_OnCommand(CommandEventArgs e)
     {
-        var eable = Map.Malas.GetItemsInRange(lp_Center, 0);
-
-        foreach (var item in eable)
+        foreach (var item in Map.Malas.GetItemsInRange(lp_Center, 0))
         {
             if (item is LeverPuzzleController)
             {