Clean up vending machines and port their visualizer (#10465)

Content.Shared/VendingMachines/VendingMachineInterfaceState.cs

@@ -0,0 +1,33 @@
+using Robust.Shared.Serialization;
+
+namespace Content.Shared.VendingMachines
+{
+    [NetSerializable, Serializable]
+    public sealed class VendingMachineInterfaceState : BoundUserInterfaceState
+    {
+        public List<VendingMachineInventoryEntry> Inventory;
+
+        public VendingMachineInterfaceState(List<VendingMachineInventoryEntry> inventory)
+        {
+            Inventory = inventory;
+        }
+    }
+
+    [Serializable, NetSerializable]
+    public sealed class VendingMachineEjectMessage : BoundUserInterfaceMessage
+    {
+        public readonly InventoryType Type;
+        public readonly string ID;
+        public VendingMachineEjectMessage(InventoryType type, string id)
+        {
+            Type = type;
+            ID = id;
+        }
+    }
+
+    [Serializable, NetSerializable]
+    public enum VendingMachineUiKey
+    {
+        Key,
+    }
+}