[FIX] web_editor: restore background videos (new imagepicker UI)

Commit [1] broke the background videos feature. This is because the
'we-imagepicker' widget is now a sub-widget of a new 'we-button-group'
widget, acting as a selection choice (same as we-button in a we-select).
When selecting a selection choice, the appropriate option method is
called, with the selection value and params... but the params were
actually the ones of the 'we-button-group' element and not the ones
of the chosen widget 'we-imagepicker'.

This has never been important for we-select widgets but it could have
been. The problem is only solved here in master, generically for all
selection widgets (currently only 'we-select' and 'we-button-group').
The params received are the ones of the active sub-widget combined with
the ones of the selection widget.

[1]: https://github.com/odoo/odoo/commit/bb0cd4d5c82a9c2311f8c45ced0e9fdc0397d292

closes odoo/odoo#54629

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_editor/static/src/js/editor/snippets.options.js

@@ -700,11 +700,19 @@ const BaseSelectionUserValueWidget = UserValueWidget.extend({
     /**
      * @override
      */
-    getValue(methodName) {
-        let activeWidget = this._userValueWidgets.find(widget => widget.isPreviewed());
+    getMethodsParams(methodName) {
+        const params = this._super(...arguments);
+        const activeWidget = this._getActiveSubWidget();
         if (!activeWidget) {
-            activeWidget = this._userValueWidgets.find(widget => widget.isActive());
+            return params;
         }
+        return Object.assign(activeWidget.getMethodsParams(...arguments), params);
+    },
+    /**
+     * @override
+     */
+    getValue(methodName) {
+        const activeWidget = this._getActiveSubWidget();
         if (activeWidget) {
             return activeWidget.getActiveValue(methodName);
         }
@@ -733,6 +741,22 @@ const BaseSelectionUserValueWidget = UserValueWidget.extend({
         }
         this._super(...arguments);
     },
+
+    //--------------------------------------------------------------------------
+    // Private
+    //--------------------------------------------------------------------------
+
+    /**
+     * @private
+     * @returns {UserValueWidget|undefined}
+     */
+    _getActiveSubWidget() {
+        const previewedWidget = this._userValueWidgets.find(widget => widget.isPreviewed());
+        if (previewedWidget) {
+            return previewedWidget;
+        }
+        return this._userValueWidgets.find(widget => widget.isActive());
+    },
 });
 
 const SelectUserValueWidget = BaseSelectionUserValueWidget.extend({