Bunch of crew AI bugfixes/improvements:

- replacing empty oxygen tanks
- fixed characters only fixing leaks in the outer hull
- prioritizing large leaks over small ones
- fixed characters doing nothing after fixing all the leaks (and sinking to the bottom if they happen to be outside)
- more accurate welder aiming
- AIObjectiveGetItem makes the characters go to the cabinet/container an item is inside, not to the actual item (which may not be actually positioned at the container)

Subsurface/Source/Items/Item.cs

@@ -466,6 +466,20 @@ namespace Barotrauma
             }
             return CurrentHull;
         }
+
+        public Item GetRootContainer()
+        {
+            if (Container == null) return null;
+
+            Item rootContainer = Container;
+
+            while (rootContainer.Container != null)
+            {
+                rootContainer = rootContainer.Container;
+            }
+
+            return rootContainer;
+        }
         
         public void AddTag(string tag)
         {