Request that the node take focus. By default, a node will
request focus using javafx.scene.Node.requestFocus().
Both JavaFX and the assisteve technology have the concept of
a focus node and most of the time, they are the same.
In some cases, a control might want the JavaFX focus to remain
on the parent, while the assistive technology focus is on the child.
For example, a table may respond to this request by setting focus
to a cell inside the table before allowing the default to run.
Used by Node, TabItem, TableCell and others
Parameters:Diagram: Accessible