[FIX] web_editor: reintroduce request_editable event

The commit fixes the display of custom colors in the color picker.

It improves previous fix from #72294, which was not returning all
editables from the editor, thus only the custom colors of the target
were displayed.
For that the request_editable event is reintroduced at the SnippetsMenu
level.

Part of https://github.com/odoo/odoo/pull/72978
task-2476601

X-original-commit: 68d7d42cce012269342e18373a30970e2c582ba3

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

@@ -1091,6 +1091,7 @@ var SnippetsMenu = Widget.extend({
         'user_value_widget_opening': '_onUserValueWidgetOpening',
         'user_value_widget_closing': '_onUserValueWidgetClosing',
         'reload_snippet_template': '_onReloadSnippetTemplate',
+        'request_editable': '_onRequestEditable',
     },
     // enum of the SnippetsMenu's tabs.
     tabs: {
@@ -3052,6 +3053,13 @@ var SnippetsMenu = Widget.extend({
     _onRedo: async function() {
         this.options.wysiwyg.redo();
     },
+    /**
+     * @private
+     * @param {OdooEvent} ev
+     */
+    _onRequestEditable: function (ev) {
+        ev.data.callback($(this.options.wysiwyg.odooEditor.editable));
+    },
 });
 
 return {