In preparation of FTUE changes... (#2556)

* Remove the welcome screen

* Allow the UserSessionFlowCoordinator to control the whole app hierarchy, not only its splitView

* Start using the new verification state listener

* Rename Onboarding to AuthenticationStart in preparation for the new OnboardingFlowCoordinator; update snapshots and tests

* Make the AuthenticationCoordinator a proper FlowCoordinator

* Add some padding around the authentication start screen report a problem button

* Bump the RustSDK to v1.1.49

* Only add bottom padding on the authentication start screen report a problem button

ElementX/Sources/Screens/Other/PlaceholderScreenCoordinator.swift

@@ -33,11 +33,11 @@ struct PlaceholderScreen: View {
     let showsBackgroundGradient: Bool
     
     var body: some View {
-        OnboardingLogo(isOnGradient: showsBackgroundGradient)
+        AuthenticationStartLogo(isOnGradient: showsBackgroundGradient)
             .frame(maxWidth: .infinity, maxHeight: .infinity)
             .background {
                 if showsBackgroundGradient {
-                    OnboardingScreenBackgroundImage()
+                    AuthenticationStartScreenBackgroundImage()
                 }
             }
             .background()