Java wrapping of external projects no longer works (VTK 8.90)
In VTK 8.2 and earlier, vtkCommonCoreJava and the other Java targets were exported via
VTKTargets.cmake. In VTK 8.90, the Java targets are no longer exported, which makes external Java wrapping impossible.
For this reason, I removed the Java wrapping from the vtkMy example in !6247 (merged). The Java targets should be re-exported and the Java wrapping code should be re-inserted into vtkMy so that external wrapping can be tested.