Allow class-based overrides to be initialized with a ScriptFunction

This is an enhancement to JDK-8011544, allowing SAM types with class-based overrides to be initialized with a script function, i.e. while we can do either of these two:

  var r1 = new java.lang.Runnable({ run: function() { print("Hello!") } })
  var r2 = new java.lang.Runnable(function() { print("Hello!") })

We can only do:

  var R1 = Java.extend(java.lang.Runnable, { run: function() { print("Hello!") } })

and not:

  var R1 = Java.extend(java.lang.Runnable, function() { print("Hello!") })

This issue restores the symmetry of being able to use a function to initialize a SAM type both in instance and class-based overrides.