Move spawning collections of EntitySpawnEntry out of StorageSystem, make Butcherable use it (#7305)

Co-authored-by: metalgearsloth <31366439+metalgearsloth@users.noreply.github.com>

Content.Server/Storage/Components/SpawnItemsOnUseComponent.cs

@@ -1,5 +1,6 @@
 using System.Collections.Generic;
 using Content.Shared.Sound;
+using Content.Shared.Storage;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Serialization.Manager.Attributes;
 
@@ -16,7 +17,7 @@ namespace Content.Server.Storage.Components
         /// </summary>
         /// <returns></returns>
         [DataField("items", required: true)]
-        public List<EntitySpawnEntry> Items = new List<EntitySpawnEntry>();
+        public List<EntitySpawnEntry> Items = new();
 
         /// <summary>
         ///     A sound to play when the items are spawned. For example, gift boxes being unwrapped.