Implement notifySpecific by using a worker exclusive thread local
sleepState and pipe.
The sleepState previously waitInflight is no longer a member of IoContext
a thread_local PipeSleepStrategy::SleepState is used instead.
It is safe to use a thread_local object because onNewWorkNotification
is only called by the Owner of the sleepState.
Since others (ANYWHERE, EMPER) must not reap newWorkNotifications from
a workers CQ.

Update the algorithm documentation and other code comments.

In a running gdb process use:

source tools/gdb/dump_runtime_state.py

to dump the state of all threads, all WSL queues and all worker IoContexts.