JAWS doesn't read FX dialogs

Reproducible: always
Is a regression: no
Platform-specific: yes, windows 10, jaws.
Looks like the reason is that fx labels are not accessible at all, but that makes dialogs not accessible (there is no way to hear message from the dialog).

Steps to reproduce:
1. Enable JAWS on windows 10 machine
2. Execute dialog demo from toys (java -cp Hello.jar hello.HelloAlert)
3. Press any button to activate dialog
Expected result: Dialog is shown, JAWS reads content of the dialog
Actual result: Dialog is shown, JAWS only reads focused "OK" button