RFR: 8311992: Test java/lang/Thread/virtual/JfrEvents::testVirtualThreadPinned failed

[Alan Bateman]

This is a test only update to a test for the JFR event jdk.VirtualThreadPinned event. The test we added in JDK 19 does 3 sleeps, one with a small duration, twice with a  long duration. The test enables the event with a threshold of 500ms and expects there will be two events recorded; no event for the sleep with the small duration. In extreme cases, it's possible that the short sleep takes more than 500ms so an event is recorded and the test fails. The test is changed to drop the threshold, it's not needed. It's also changed to explicitly park to avoid the long sleeps. A drive-by change is to print the events to System.err rather than System.out so they are inlined with the JUnit output (the original test was TestNG where the output went to System.out).

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Commit messages:
 - Improve test
 - Merge
 - Initial commit

Changes: https://git.openjdk.org/jdk/pull/14884/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=14884&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8311992
  Stats: 42 lines in 1 file changed: 19 ins; 2 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/14884.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14884/head:pull/14884

PR: https://git.openjdk.org/jdk/pull/14884