Add warning about WCF service IOCP thread pool usage to Timeouts.md

The WCF service may scale up slowly under load article documents that "WCF uses the .NET CLR IOCP thread pool for executing your WCF service code." As a result, performing synchronous blocking I/O, wait, or maybe even CPU-bound operations in a WCF service can easily lead to IOCP thread pool exhaustion that can result in timeouts for unrelated I/O operations.

The article provides "steps to implement [a] solution that will execute the WCF service on the .NET CLR Worker thread pool" using a new WorkerThreadPoolBehaviorAttribute. I can confirm that this workaround is very effective at resolving the IOCP thread pool exhaustion issues caused by WCF services.

When using WCF services, I would recommend trying the above workaround before manually configuring the IOCP tread pool limits.

I think the above information would be helpful to be added to Timeouts.md, but I am not sure about the best format as the Are you seeing a high number of busyio or busyworker threads in the timeout exception? section is already very long.

Start with docs/Timeouts.md and review the “Are you seeing a high number of busyio or busyworker threads in the timeout exception?” section, then read the linked Microsoft WCF article. Add a concise warning about WCF IOCP thread-pool exhaustion and link to the WorkerThreadPoolBehaviorAttribute workaround; done when the guidance is clear and fits the existing section.