LiveView Native Clients: Use uniffi bindings for uses of liveview-native-core-swift

[simlay]

With liveview-native/liveview-native-core#43, we can move away from hand written bindings in https://github.com/liveview-native/liveview-native-core-swift/. There are some changes required for this transition.

[AZholtkevych]

@carson-katri @nelson-glauber would you mind reviewing those PRs, please?