GraalJSScriptEngine implements Invocable, which is why casting to it works.
However, this is just a quick and ugly fix to make it compile.
A better solution would be to cast it once, immediately after `eval`,
and from then on only handle it as Invocable.
Scripts still need to be fixed. They are still using Rhino and Nashorn-specific
ways of importing packages.
Usages of "importPackage" and "Packages" need to be replaced with
the Graal specific "Java.type".
