ForkJoinPool-3-worker pool size never size down

[何品(虎鸣)]

Hi I know, it was suggested that not pooling the VirtualThread, when I replace my old executors to use the fancy new `VirtualThreadExecutorFactory` and with the 
`jdk.virtualThreadScheduler.maxPoolSize` set to 2500
after some load testing and the thread size grow to 2205 
and even the stress testing is removed from the system , the thread never adjust to a smaller one. 
I will change my code to not pooling the virtual thread then.
eg:
"ForkJoinPool-3-worker-2173" Id=51031 WAITING on java.util.concurrent.ForkJoinPool at 20ccd17 at java.base at 21.0.1.0.1/jdk.internal.misc.Unsafe.park(Native Method) - waiting on java.util.concurrent.ForkJoinPool at 20ccd17 at java.base at 21.0.1.0.1/java.util.concurrent.locks.LockSupport.park(LockSupport.java:371) at java.base at 21.0.1.0.1/java.util.concurrent.ForkJoinPool.awaitWork(ForkJoinPool.java:1893) at java.base at 21.0.1.0.1/java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1809) at java.base at 21.0.1.0.1/java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:188)
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