Support custom thread pool metrics collection.

[ixiaoyi93]

Is your feature request related to a problem? Please describe.

It is not possible to collect thread pools customized by ThreadPoolExecutor. The code example is as follows:

Describe the solution you'd like

Supports custom thread pool monitoring implemented by the following thread pool frameworks:

• java.util.ThreadPoolExecutor: Generally used in Tomcat8~9.1, Dubbo, HSF, Vertx and user-defined thread pools.
• org.apache.tomcat.util.threads.ThreadPoolExecutor: Generally used in Tomcat9.1+.
• org.eclipse.jetty.util.thread.QueuedThreadPool: Generally used in Jetty.
• org.xnio.XnioWorker: Generally used in Undertow.

Describe alternatives you've considered

No response

Additional context

No response