RFR: JDK-8151726: Introduce a JPRT testset buildinfra

[Erik Joelsson]

When verifying build changes, we are currently lacking a good way of 
doing all relevant builds in one JPRT job. Some build configurations we 
aren't even able to test at all. To facilitate this, I would like to 
introduce a new testset. This testset will be a super set of the current 
default testset and hotspot and then some more.

This patch also adds a bunch of Jib profiles to support these build 
configurations. The most important for developers is that all main 
platforms now have a Jib profile for slowdebug.

Bug: https://bugs.openjdk.java.net/browse/JDK-8151726
Webrev: http://cr.openjdk.java.net/~erikj/8151726/webrev.01/

/Erik