Make viewmodels consistent with UI objects

[anuragshukla06]

Currently, each scenario/fragments each have its own state-holder class. This is simply a code repetition and is inconsistent in many places.

[thedroiddiv]

Instead of having a <Fragment>UiState class separately for each UiState, we can have a common generic class like

sealed class UiState<T>(
    val data: T? = null,
    val message: String? = null
) {
    class Success<T>(data: T) : UiState<T>(data)
    class Error<T>(message: String?, data: T? = null) : UiState<T>(data, message)
    class Loading<T> : UiState<T>()
    class Initial<T> : UiState<T>()
}

Where T would be the type of result we would be expecting. And then we can use this wrapper everywhere, thus maintaining the consistency.

[thedroiddiv]

Can be parallelly done with compose migration, so currently blocked by that.