[FIX] web_editor: prevent dropping popup inside a substructure

Before this commit, it was possible to drag and drop a popup inside an
oe_structure which was itself inside an other oe_structure (e.g. snippet
parallax). It didn't make sense and moreover created bugs.

After this commit, it is no longer possible to drag and drop the popup
snippet or the newsletter popup snippet in a substructure.

task-2491976

closes odoo/odoo#81669

X-original-commit: 49050c124795852ce7ad51b92958498972730dcf
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>
Co-authored-by: qsm-odoo <qsm@odoo.com>

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

@@ -2375,6 +2375,13 @@ var SnippetsMenu = Widget.extend({
                         }
                     }
 
+                    // TODO mentioning external app snippet but done as a stable fix
+                    // that will be adapted in master: if popup snippet, do not
+                    // allow to add it in another snippet
+                    if ($baseBody[0].matches('.s_popup, .o_newsletter_popup')) {
+                        $selectorChildren = $selectorChildren.not('[data-snippet] *');
+                    }
+
                     $toInsert = $baseBody.clone();
                     // Color-customize dynamic SVGs in dropped snippets with current theme colors.
                     [...$toInsert.find('img[src^="/web_editor/shape/"]')].forEach(dynamicSvg => {