RFR 8158736: Adapter class loaders can avoid creating named dynamic modules

[Sundararajan Athijegannathan]

Please review: http://cr.openjdk.java.net/~sundar/8158736/webrev.00/ for
https://bugs.openjdk.java.net/browse/JDK-8158736

Nashorn creates named, dynamic modules for java adapter classes. This
can be avoided and we can use the default, unnamed module created for
the adapter class loader. Nashorn allows only subtyping of public,
exported supertypes be implemented in scripts.  The only package used in
adapter module is exported and the adapter type is public as well.

There is no need for named dynamic module - as there is nothing to
encapsulate.  Nashorn module can still selectively export packages to
adapter module [ so that generated adapter class can access nashorn
internals as needed].

This avoids having to generate read-links to the modules of the
reference types used by the adapter class - because unnamed adapter
module has read edges to all the modules.

Thanks,

-Sundar