chore: remove unused classes of views API (#22861)

* chore: remove unused views API classes

* chore: remove LayoutManager code

* chore: no more need to make View inherit from TrackabeObject

* chore: make enable_view_api default to true

* chore: enable_view_api => enable_views_api

lib/browser/api/module-keys.js

@@ -42,12 +42,6 @@ module.exports = [
 
 if (features.isViewApiEnabled()) {
   module.exports.push(
-    { name: 'BoxLayout' },
-    { name: 'Button' },
-    { name: 'LabelButton' },
-    { name: 'LayoutManager' },
-    { name: 'MdTextButton' },
-    { name: 'ResizeArea' },
-    { name: 'TextField' }
+    { name: 'ImageView' }
   );
 }