RFR [15] (T/XS): 8242388 compiler/graalunit/CoreTest.java timed out

[Ekaterina Pavlova]

Hi all,

compiler/graalunit/CoreTest.java fails by timeout from time to time.
The most time expensive subtest is org.graalvm.compiler.core.test.CountedLoopTest.
The fix spits the test into two tests to reduce total execution time.
Please review.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8242388
  webrev: http://cr.openjdk.java.net/~epavlova//8242388/webrev.00/index.html
testing: graalunit tests as part of tier3


Thanks,
-katya