8199271: [TESTBUG] open source VM testbase stress tests

[Leonid Mesnik]

Hi

Please review this change open sourcing vm testbase stress tests. These tests have been developed a long time ago for internal test harness and don't looks very nice now.
They are open sourced with minimal changes only. The long term plan is to review and improve them moving out of vmTestbase directory in corresponding components.

The fix introduce vmTestbase_nsk_stress test group and have make files changes required to build native part of tests.

I've verified that "make -- run-test TEST=:vmTestbase_nsk_stress" pass on my linux locally. 

webrev: http://cr.openjdk.java.net/~lmesnik/8199271/webrev.00/ <http://cr.openjdk.java.net/~lmesnik/8199271/webrev.00/>
bug: https://bugs.openjdk.java.net/browse/JDK-8199271 <https://bugs.openjdk.java.net/browse/JDK-8199271>