Fixes #4374 - Nukes all (?) legacy Driver and Application stuff; revamps tests (#4376)

Tests/UnitTests/View/Draw/NeedsDrawTests.cs

@@ -37,7 +37,7 @@ public class NeedsDrawTests ()
 
         top.Add (frame);
 
-        RunState runState = Application.Begin (top);
+        SessionToken sessionToken = Application.Begin (top);
 
         Application.Driver!.SetScreenSize (80,25);
 
@@ -62,7 +62,7 @@ public class NeedsDrawTests ()
                      );
         Assert.Equal (new (0, 0, 30, 1), label.Frame);
         Assert.Equal (new (0, 1, 9, 1), view.Frame); // this proves frame was set
-        Application.End (runState);
+        Application.End (sessionToken);
         top.Dispose ();
     }
 }