migrate to java 11: add casts to raw types to workaround changes in generic signatures of some swing methods

Types of some members in Swing API were generified in Java 11 (e.g. DefaultMutableTreeNode::children, DefaultTableModel::getDataVector) so we need to add explicit cast to raw types to makes usages of these members compilable.

GitOrigin-RevId: 011d032c0ffe7d51c533921c230df64396b19597