feat: rework Pause

Now a dialog.

* Also fix the new BetterGiveUp panic restart
* Also move SortByInternal's PNG away from the root namespace

Extras/SortByInternalDifficulty/MU3/patch_UISortButton.cs

@@ -22,7 +22,7 @@ class patch_UISortButton: UISortButton {
         }
 
         Texture2D tex = new Texture2D(2, 2);
-        tex.LoadImage(InternalSortPreview.Bytes);
+        tex.LoadImage(Mod.InternalSortPreview.Bytes);
 
         newSprites[n] = Sprite.Create(tex, new Rect(0, 0, 254, 121), newSprites[0].pivot);