Unit tests for SwingFXUtils.fromFXImage

Issue RT-36854 has some test programs attached to it that should be added as unit tests for the SwingFXUtils package. Two changes need to happen to get there:

- SwingFXUtils has no test hierarchy in the current builds so one would need to be added
- The tests are slightly too manual in their current state to be used as unit tests and would need a way to make the test images pre-generated, or to generate them on the fly as the tests run