TF-4370 Add E2E test for test case create new a tag

lib/features/labels/presentation/widgets/create_new_label_modal.dart

@@ -281,6 +281,7 @@ class _CreateNewLabelModalState extends State<CreateNewLabelModal> {
       valueListenable: _labelNameErrorTextNotifier,
       builder: (_, errorText, __) {
         return LabelInputFieldBuilder(
+          key: const Key('label_name_input_field'),
           label: appLocalizations.labelName,
           hintText: appLocalizations
               .pleaseEnterNameYourNewLabel,
@@ -309,6 +310,7 @@ class _CreateNewLabelModalState extends State<CreateNewLabelModal> {
 
   Widget _buildLabelDescriptionInputField(AppLocalizations appLocalizations) {
     return LabelInputFieldBuilder(
+      key: const Key('label_description_input_field'),
       label: appLocalizations.labelDescription,
       hintText: appLocalizations.labelDescriptionHintText,
       textEditingController: _descriptionInputController,

lib/features/mailbox/presentation/widgets/labels/labels_bar_widget.dart

@@ -35,6 +35,7 @@ class LabelsBarWidget extends StatelessWidget {
   @override
   Widget build(BuildContext context) {
     Widget addNewLabelIcon = TMailButtonWidget.fromIcon(
+      key: const Key('labels_bar_widget_add_new_label_button'),
       icon: imagePaths.icAddNewFolder,
       backgroundColor: Colors.transparent,
       iconColor: AppColor.steelGrayA540,