Update to 1.20

- Use GuiGraphics for rendering UI elements. Almost definitely some
   z-fighting issues slipped in here.

 - Use Forge's loot modifier system for handling treasure disks. I have
   mixed feelings about this - it's a nice system, but also is far less
   efficient than the previous approach.

 - Regenerate data. This is the brunt of the commit, but nothing
   especially interesting here.

projects/common/src/test/java/dan200/computercraft/TestPlatformHelper.java

@@ -165,11 +165,9 @@ public class TestPlatformHelper extends AbstractComputerCraftAPI implements Plat
         throw new UnsupportedOperationException("Cannot interact with the world inside tests");
     }
 
-
-    @Nullable
     @Override
-    public ResourceLocation getCreativeTabId(CreativeModeTab tab) {
-        return null;
+    public CreativeModeTab.Builder newCreativeModeTab() {
+        throw new IllegalStateException("Cannot create creative tab inside tests");
     }
 
     @Override