RFR(XS): 8229210: [TESTBUG] Move gc stress tests from JFR directory tree to gc/stress

[mikhailo.seledtsov at oracle.com]

Please review this change that simply moves GC+JFR stress tests from 
test/jdk/jdk/jfr/event/gc/detailed/TestStress*
to test/hotspot/jtreg/gc/stress/jfr/

This change was originated by JFR team, and later informally discussed 
with GC team members. The goal is to remove
heavy time-consuming GC event stress tests from JFR hierarchy to 
GC/stress, where they better fit.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8229210
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8229210.00/
        Just a simple move, no changes to the tests:
        hg mv test/jdk/jdk/jfr/event/gc/detailed/TestStress* 
test/hotspot/jtreg/gc/stress/jfr/

     Testing:
         1. Sanity: Ran test/hotspot/jtreg/gc/stress/jfr/ - PASS
         2. Sanity: running jdk_jfr - in progress


Thank you,
Misha