[IMP] web: propagate "on_attach_callback" to all widgets in form renderer

Co-authored-by: twa-odoo <twa@odoo.com>

closes odoo/odoo#27711

addons/web/static/src/js/views/form/form_renderer.js

@@ -223,6 +223,15 @@ var FormRenderer = BasicRenderer.extend({
             }
         });
     },
+    /**
+     * Called each time the form view is attached into the DOM
+     */
+    on_attach_callback: function () {
+        _.forEach(this.allFieldWidgets, function (widgets){
+            _.invoke(widgets, 'on_attach_callback');
+        });
+        this._super.apply(this, arguments);
+    },
     /**
      * @override method from AbstractRenderer
      * @param {Object} state a valid state given by the model