VirtualThread stress test PingPong times out

[andrew-m-leonard]

java/lang/Thread/virtual/stress/PingPong.java (SQ and LTQ) tests by default perform 500,000 iterations,
see: https://github.com/openjdk/jdk21u/blob/eced83e13090748218ab3dac78f6ff1bddf2b158/test/jdk/java/lang/Thread/virtual/stress/PingPong.java#L28
this typically far exceeds the default 15 minutes openjdk jtreg timeout

On a typical Windows machine it achieves around 30,000 in 15 minutes before timing out.

These two tests need an additional "iterations" parameter with a lower value to run within the 15 minutes.
Note, this has been seen failing on other platforms too, eg:aarch64_linux.

ref:adoptium/ci-jenkins-pipelines#1104 (comment)