Summary
-------

Add `sealed` to the class signature of `java.io.Console` class declaration

Problem
-------

With the change to [JDK-8295803][1], `java.io.Console` class removed `final` classifier, thus it is possible to have an arbitrary subclass in the java.io package. Limiting this to known internal implementations improves platform integrity.

Specification
-------------

Change the declaration of `java.io.Console` class from
```
public class Console implements Flushable
```
to
```
public sealed class Console implements Flushable permits ClassA, ClassB, ...
```
*ClassA, ClassB, ...: package private classes in `java.io`. Names to be defined*


  [1]: https://bugs.openjdk.org/browse/JDK-8295803