LibGUI: Add AbstractView::editing_rect() to allow custom editing rects

This allows view classes to customize the editing rect for an index.

Userland/Libraries/LibGUI/AbstractView.cpp

@@ -147,7 +147,7 @@ void AbstractView::begin_editing(const ModelIndex& index)
     m_edit_widget = m_editing_delegate->widget();
     add_child(*m_edit_widget);
     m_edit_widget->move_to_back();
-    m_edit_widget_content_rect = content_rect(index).translated(frame_thickness(), frame_thickness());
+    m_edit_widget_content_rect = editing_rect(index).translated(frame_thickness(), frame_thickness());
     update_edit_widget_position();
     m_edit_widget->set_focus(true);
     m_editing_delegate->will_begin_editing();

Userland/Libraries/LibGUI/AbstractView.h

@@ -89,6 +89,8 @@ public:
     virtual void did_update_selection();
 
     virtual Gfx::IntRect content_rect(const ModelIndex&) const { return {}; }
+    virtual Gfx::IntRect editing_rect(ModelIndex const& index) const { return content_rect(index); }
+
     virtual ModelIndex index_at_event_position(const Gfx::IntPoint&) const { return {}; }
     void begin_editing(const ModelIndex&);
     void stop_editing();