Motivation:
swift- nio was failing builds that should pass
Modifications:
Adding available to the necessary sections
* Updating test OnToRunClosure
Motivation:
testCancelledScheduledTasksDoNotHoldOnToRunClosure() was not allowed enough time and timing off at moments, causing it to fail occasionally
Modifications:
Added a ConditionLock throughout the code to make sure it only unlocks when the code has waited enough time for it to not hit the precondition failure
### Motivation:
In my previous PR https://github.com/apple/swift-nio/pull/2010, I was able to decrease the allocations for both `scheduleTask` and `execute` by 1 already. Gladly, there are no more allocations left to remove from `execute` now; however, `scheduleTask` still provides a couple of allocations that we can try to get rid of.
### Modifications:
This PR removes two allocations inside `Scheduled` where we were using the passed in `EventLoopPromise` to call the `cancellationTask` once the `EventLoopFuture` of the promise fails. This requires two allocations inside `whenFailure` and inside `_whenComplete`. However, since we are passing the `cancellationTask` to `Scheduled` anyhow and `Scheduled` is also the one that is failing the promise from the `cancel()` method. We can just go ahead and store the `cancellationTask` inside `Scheduled` and call it from the `cancel()` method directly instead of going through the future.
Importantly, here is that the `cancellationTask` is not allowed to retain the `ScheduledTask.task` otherwise we would change the semantics and retain the `ScheduledTask.task` longer than necessary. My previous PR https://github.com/apple/swift-nio/pull/2010, already implemented the work to get rid of the retain from the `cancellationTask` closure. So we are good to go ahead and store the `cancellationTask` inside `Scheduled` now
### Result:
`scheduleTask` requires two fewer allocations
Motivation:
EmbeddedChannel is an important testing tool, and we want to use it
without needing to bring along the POSIX layer. They are not tightly
coupled. However, it also doesn't belong naturally in NIOCore, so we
should probably put it in its own place.
Modifications:
- Moved EmbeddedChannel and EmbeddedEventLoop to NIOEmbedded.
- Moved the tests to NIOEmbeddedTests
- Duplicated some test helpers
Result:
Easy to use EmbeddedChannel without the POSIX layer.
carolinacass