`Unconfined` is potentially very dangerous and sho...

# coroutines

[elizarov]

Unconfined is potentially very dangerous and should be handled with extreme care. As a rule of thumb, you should use Unconfined only if you cannot use any other confined alternative or as a means of performance optimization. Make sure, though, that you do not optimize prematurely without a definite proof that you experience any dispatching-related performance problems.