Shared Containers (#3331)

* Namespace changes for containers.
Moved ContainerSlot from content to engine.

* Merged client/server ContainerManagerComponents into a single shared version.

* Mapfile and nullability fixes.

* Upgrades map.

* Update engine.

Content.Server/GameObjects/Components/GUI/HandsComponent.cs

@@ -457,7 +457,7 @@ namespace Content.Server.GameObjects.Components.GUI
                 throw new InvalidOperationException($"Hand '{name}' already exists.");
             }
 
-            var container = ContainerManagerComponent.Create<ContainerSlot>($"hand {_nextHand++}", Owner);
+            var container = ContainerHelpers.CreateContainer<ContainerSlot>(Owner, $"hand {_nextHand++}");
             var hand = new Hand(this, name, container);
 
             _hands.Add(hand);

Content.Server/GameObjects/Components/GUI/HumanInventoryControllerComponent.cs

@@ -1,5 +1,6 @@
 using Content.Server.GameObjects.Components.Items.Storage;
 using Robust.Server.GameObjects;
+using Robust.Shared.Containers;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Localization;
 using static Content.Shared.GameObjects.Components.Inventory.EquipmentSlotDefines;

Content.Server/GameObjects/Components/GUI/InventoryComponent.cs

@@ -426,7 +426,7 @@ namespace Content.Server.GameObjects.Components.GUI
 
             Dirty();
 
-            _slotContainers[slot] = ContainerManagerComponent.Create<ContainerSlot>(GetSlotString(slot), Owner);
+            _slotContainers[slot] = ContainerHelpers.CreateContainer<ContainerSlot>(Owner, GetSlotString(slot));
 
             OnItemChanged?.Invoke();