RFR: JDK-8189682: JDK demos/tests should be in a separate bundle than hotspot ones

[Erik Joelsson]

This patch adds building of a new test bundle containing just the 
remaining demos, which are used for client testing. It's basically 
resurrecting the build logic for the old demo bundles, but adding tests 
to the bundle name to make the intent clear. It's also a tar.gz on all 
platforms.

Bug: https://bugs.openjdk.java.net/browse/JDK-8189682
Webrev: http://cr.openjdk.java.net/~erikj/8189682/webrev.01/

/Erik