A counting semaphore for coroutines that logically maintains a number of available permits. Each acquire takes a single permit or suspends until it is available. Each release adds a permit, potentially releasing a suspended acquirer. Semaphore is fair and maintains a FIFO order of acquirers.
Semaphores are mostly used to limit the number of coroutines that have access to particular resource. Semaphore with permits = 1 is essentially a Mutex.
Releases a permit, returning it into this semaphore. Resumes the first suspending acquirer if there is one at the point of invocation. Throws IllegalStateException if the number of release invocations is greater than the number of preceding acquire.