Deprecate callback APIs in favor of Swift 5.5 concurrency

[Saklad5]

Swift 5.5’s new concurrency system is designed to be a drop-in replacement for callback APIs, and improves upon them considerably. As such, you should consider adopting it as soon as possible.

One of the benefits of the new concurrency system is the ability to overload a method with synchronous and asynchronous implementations. This means you can use the same name for both, which is considered best practice going forward.