Summary
-------

Terminally deprecate the RMI Activation mechanism.

Problem
-------

The RMI Activation mechanism is an obsolete part of RMI that has been
optional since Java 8. It is effectively obsolete; it is disused; and it imposes
a maintenance burden on the JDK. See JEP 385 (JDK-8244917) for
additional information.

Solution
--------

Terminally deprecate the RMI Activation mechanism, including the
`java.rmi.activation` package, including the public, top-level classes and interfaces
it contains. Also deprecate the `rmid` tool.

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

Zip files of the webrev and specdiff of corresponding changes to the specification
are attached. The specdiff is rather difficult to read, as it is cluttered by the boilerplate
deprecation text added by javadoc. A brief summary of the specification changes is as follows:

 - add a deprecation notice to the `java.rmi.activation` package specification
 - add a deprecation notice to the `java.rmi` module specification
 - add the annotation `@Deprecated(forRemoval=true, since="15")` to each public, top-level
   class or interface in the `java.rmi.activation` package