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/Items/Addons/SHTeleporter.cs

@@ -1,4 +1,3 @@
-using System.Linq;
 using ModernUO.Serialization;
 using Server.Mobiles;
 
@@ -268,9 +267,15 @@ namespace Server.Items
 
             public static SHTeleporter FindSHTeleporter(Map map, Point3D p)
             {
-                var eable = map.GetItemsInRange<SHTeleporter>(p, 0);
-                var teleporter = eable.FirstOrDefault(item => item.Z == p.Z);
-                return teleporter;
+                foreach (var teleporter in map.GetItemsInRange<SHTeleporter>(p, 0))
+                {
+                    if (teleporter.Z == p.Z)
+                    {
+                        return teleporter;
+                    }
+                }
+
+                return null;
             }
 
             public SHTeleporter AddSHT(Map map, bool ext, int x, int y, int z)

Projects/UOContent/Items/Construction/Doors/BaseDoor.cs

@@ -332,13 +332,10 @@ public abstract partial class BaseDoor : Item, ILockable, ITelekinesisable
         var z = p.Z;
 
         var sector = map.GetSector(x, y);
-        var items = sector.Items;
         var mobs = sector.Mobiles;
 
-        for (var i = 0; i < items.Count; ++i)
+        foreach (var item in sector.Items)
         {
-            var item = items[i];
-
             if (item is not BaseMulti && item.ItemID <= TileData.MaxItemValue && item.AtWorldPoint(x, y) &&
                 item is not BaseDoor)
             {

Projects/UOContent/Items/Containers/MarkContainer.cs

@@ -130,15 +130,14 @@ public partial class MarkContainer : LockableContainer
 
     private static bool FindMarkContainer(Point3D p, Map map)
     {
-        var eable = map.GetItemsInRange<MarkContainer>(p, 0);
-
-        foreach (var item in eable)
+        foreach (var item in map.GetItemsInRange<MarkContainer>(p, 0))
         {
             if (item.Z == p.Z)
             {
                 return true;
             }
         }
+
         return false;
     }
 

Projects/UOContent/Items/Misc/OilFlask.cs

@@ -49,9 +49,8 @@ public partial class OilFlask : Item
             if (!from.PlaceInBackpack(emptyFlask))
             {
                 var didStack = false;
-                var eable = from.GetItemsInRange(0);
 
-                foreach (var i in eable)
+                foreach (var i in from.GetItemsInRange(0))
                 {
                     if (i.StackWith(from, this, false))
                     {