Determines if given java file contains the "jbInit" method for the legacy UI editor.
If this method is not present, there should be no Design tab offered for the java file
in editor. This rule should be only used by the UI editor at the moment the
JavaSourceNode is about to open. At that moment the node is selected in app navigator
and already parsed for the Structure window, so looking for a method via JOT as part
of the editor opening should not be expensive.