Add simple Producer/Consumer microbenchmark for Thread.onSpinWait

From https://mail.openjdk.java.net/pipermail/hotspot-dev/2021-August/054033.html:

"a SynchronousQueue microbenchmark (you can find it in https://bugs.openjdk.java.net/browse/JDK-8267502).... The SynchronousQueue microbenchmark, which uses Thread.onSpinWait, got 2.9x improvement."

Since jdk17 java.util.concurrent.SynchronousQueue has not been using Thread.onSpinWait. Because of this the microbenchmark shows no improvements.

A microbenchmark for the approach used in jdk11 java.util.concurrent.SynchronousQueue can be added.