Set the old widget parent to None when changing the layout widget.
Move the custom layout event to a new module. This cleans up imports.
Take responsibility for raising the frame in the docking Z-order
Reuse the single widget layout for the dock frame layout.
Update layout and close event handling.
Update layout handling and take responsibility for unplugging the layout.
Handle the close event for the dock item
Simplify the manager for the new behavior performed by the dock frames
Collapse relayout requests on a single shot timer