ActivityScenario: Custom instanciation

### Description
The `launch(Activity)` method can't be customized very well, especially compared to launchFragmentInContainer / FragmentScenario. That makes it particularly hard to test / verify code that happens during onCreate(). In our example, a MainActivity (that contains the NavHostFragment for Jetpack Navigation) navigates to an on-boarding screen on first start.
Verifying this code is hard with the current ActivityScenario as the initial state can't be controlled and thus we can't properly mock / spy the navigation controller (Compared to [how it can be done with FragmentScenario](https://developer.android.com/guide/navigation/navigation-testing#test_navigationui_with_fragmentscenario)).

### Expected Results
Ideally, `launch(Activity)` take a custom `ActivityFactory` or Lambda like `launchFragmentInContainer` that allows to customize activity creation. A convenience parameter to decide which state to launch into (i.e. CREATED, RESUMED) won't hurt either.

### Link to a public git repo demonstrating the problem:
See https://issuetracker.google.com/issues/139695101

### Versions

testImplementation("androidx.arch.core:core-testing:2.0.1")
testImplementation("androidx.test.espresso:espresso-core:3.2.0")
testImplementation("androidx.test.ext:junit-ktx:1.1.1")
testImplementation("io.mockk:mockk:1.9.3")
testImplementation("org.robolectric:robolectric:4.3")

Inizia dal punto di ingresso ActivityScenario.launch(Activity) e confronta le sue opzioni di personalizzazione con launchFragmentInContainer e FragmentScenario. Definisci come dovrebbero funzionare una ActivityFactory personalizzata e uno stato iniziale opzionale CREATED o RESUMED, quindi aggiungi la copertura per la creazione di Activities personalizzate e per uno stato del ciclo di vita controllato.

Scritto dal modello di indicizzazione a partire dal testo della issue.