Open-source simple test programs for FX / Swing interop

We have three simple test programs that are used during integration testing:

HelloJFXPanel - a simple Swing test app with a JButton and a JFXPanel containing an animated rectangle

HelloJFXPanels - a simple Swing test app with a JButton and a JFXPanel containing a JavaFX Button and ComboBox (with Tooltips)

EmbeddedSwing - a simple FX test app with a SwingNode containing a Swing application

These three program should be open-sourced and moved to the apps/toys directory in the "rt" repo.