Rewrite navigation using NavigationStack

[stefanceriu]

We are currently using the NavigationRouter UIKit component imported from Element to handle navigation in ElementX. We would like to move away from that and switch to a more SwiftUI approach using the newly introduced NavigationStack

We would still need to preserve the decoupling through MVVM-C so we need to use the NavigationStack to implement something that suits us.

We will also probably need to rewrite the toats and indicators, ideally revisiting their architecture.