[Pitch] Task cancellation scopes

Hi everyone, @ktoso and I have written a pitch for what we call "task cancellation scopes". We have used these as an implementation detail of withDeadline but found multiple motivating use-cases that make us believe they are generally useful. We would love to hear your feedback on this pitch. Below is the full pitch copied from Task cancellation scopes by FranzBusch · Pull Request #3533 · swiftlang/swift-evolution · GitHub Task cancellation scopes Summary of changes Introduces withTaskCancell...