Create UITesting target with:
- AppCommandLine/AppEnvironment: strongly typed refactoring of PP_*
environment values
- AccessibilityInfo: identifies and locates elements for UI testing
Make the app behave differently when launched with `.uiTesting`, and
expose the flag to SwiftUI via `.environment(\.isUITesting)` to:
- Use the mock AppContext
- Skip onboarding
Add PassepartoutUITests target with two screenshot tests:
- Connected screen
- Profile modal
Davide