Refactor: move disposing properties into the base class (#33740)

Moves more functionality to `base-component`, transferring the responsibility of disposal to parent class.
Each component, dusting disposal, sets its protected properties to `null`. So the same can be done in one place for all children components .

js/src/toast.js

@@ -144,7 +144,6 @@ class Toast extends BaseComponent {
     }
 
     super.dispose()
-    this._config = null
   }
 
   // Private