Before this diff, we wrapped all registration screens with a SafeAreaView in RegistrationNavigator.

However, this meant that the SIWEPanel background had a sharp cutoff at the SafeAreaView bounds.

In order to allow the SIWEPanel to appear over the SafeAreaView, this diff moves responsibility for rendering SafeAreaView to the individual screens. This is achieved with a new RegistrationContainer component.

Depends on D7844