Cooperatively yields execution to local Rayon work.
If the current thread is part of a rayon thread pool, this looks for a single unit of pending work in this thread’s queue, then executes it. Completion of that work might include nested work or further work stealing.
This is similar to
yield_now(), but does not steal from other threads.
Some(Yield::Executed) if anything was executed,
nothing was available, or
None if this thread is not part of any pool at all.