Use Decompose for navigation

[arkivanov]

As discussed with @kpgalligan, here is a PR demonstrating the integration of Decompose. That's a lot of code. All ViewModels a replaced with Components. The navigation is entirely handled by Decompose, plus there are some fancy animations. I have tested the Android app with Compose UI, and the iOS app with SwiftUI. I couldn't test the iOS app with Compose for iOS for some technical reasons - Compose for iOS currently crashes at runtime on my specific machine (some hardware issues), but it does compile just fine. I will appreciate if someone verify how it actually works, I guess it should be fine.