Backported vsync changes from new-netcode, WIP hull visibility culling

The hull culling functions are there, they just aren't being used right now because there are some annoying bugs.

Subsurface/Source/Items/FixRequirement.cs

@@ -186,18 +186,23 @@ namespace Barotrauma
         }
 
         public static void DrawHud(SpriteBatch spriteBatch, Item item, Character character)
+        {
+            if (frame == null) return;
+
+            frame.Draw(spriteBatch);
+        }
+
+        public static void UpdateHud(Item item, Character character)
         {
             if (frame == null || frame.UserData != item)
             {
                 CreateGUIFrame(item);
-                
             }
             UpdateGUIFrame(item, character);
 
             if (frame == null) return;
 
             frame.Update((float)Physics.step);
-            frame.Draw(spriteBatch);
         }
     }
 }