Bring WaterfallExecutor logging on par with RunnableConsumerThreadPool

Ronny noticed the other day that the trick documented in the Performance Tuning wiki article to count alive poller threads no longer works in 1.12. I dug in a bit and found that the RunnableConsumerThreadPool is gone now, seemingly replaced with WaterfallExecutor. I haven't studied the new class structure but presumably it still uses a thread pool in a roughly comparable way. Can we put in a similar log message, or document in the wiki whatever existing message people should be looking for instead?

2007-09-05 10:30:32,755 DEBUG [PollerScheduler-45 Pool] RunnableConsumerThreadPool$SizingFifoQueue:
adjust: started fiber PollerScheduler-45 Pool-fiber2 ratio = 1.0227273, alive = 44