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/Morgue/MorgueEntityStorageComponent.cs

@@ -9,6 +9,7 @@ using Content.Shared.Interfaces.GameObjects.Components;
 using Content.Shared.Physics;
 using Content.Shared.Utility;
 using Robust.Server.GameObjects;
+using Robust.Shared.Containers;
 using Robust.Shared.GameObjects;
 using Robust.Shared.Localization;
 using Robust.Shared.Maths;
@@ -46,7 +47,7 @@ namespace Content.Server.GameObjects.Components.Morgue
         {
             base.Initialize();
             Appearance?.SetData(MorgueVisuals.Open, false);
-            TrayContainer = ContainerManagerComponent.Ensure<ContainerSlot>("morgue_tray", Owner, out _);
+            TrayContainer = ContainerHelpers.EnsureContainer<ContainerSlot>(Owner, "morgue_tray", out _);
         }
 
         /// <inheritdoc />