Create new ToolbarButton type for Layout Selector; wire up custom UI; prep for viewportGridService usage

extensions/vtk/src/toolbarModule.js

@@ -128,7 +128,9 @@ const definitions = [
   },
 ];
 
-export default {
-  definitions,
-  defaultContext: 'ACTIVE_VIEWPORT::VTK',
-};
+export default [];
+
+// export default {
+//   definitions,
+//   defaultContext: 'ACTIVE_VIEWPORT::VTK',
+// };