TextEditor: Introduce a *Widget::activateEditor signal

For communication with the EditorManager without explicitly
using the editor() member.

Change-Id: I89882201924682111365b28804aed28c967bd442
Reviewed-by: Christian Stenger <christian.stenger@digia.com>

src/plugins/texteditor/basetexteditor.cpp

@@ -7337,6 +7337,9 @@ BaseTextEditor *BaseTextEditorFactory::createEditorHelper(const BaseTextDocument
                 editor->markTooltipRequested(editor, globalPos, line);
             });
 
+    connect(widget, &BaseTextEditorWidget::activateEditor,
+            [editor]() { Core::EditorManager::activateEditor(editor); });
+
     widget->finalizeInitialization();
     editor->finalizeInitialization();