Update the deprecated used methods on iOS/MacOS

[Abedalkareem]

We are using some deprecated methods on the iOS implementation so I think we should migrate to the new methods and along the way we should use async and await.

The one and the only limitation is that we need to upgrade the minimum supported os to iOS 14.

[Abedalkareem]

I'm moving also all iOS/macOS code to the Darwin folder as mentioned here.

[theLee3]

When we implement this, we should also migrate to Swift Package Manager, future-proofing while maintaining backwards compatibility, as noted here.

Are you working on this? Or would you like for me to take it on?

[Abedalkareem]

Done in #203