Tweaks to Onboarding following design review.

Use constants for consistent top padding and icon sizes.
Match layout of AnalyticsPrompt on iPad to other views.
Update icon in use case selection screen to allow tinting.

RiotSwiftUI/Modules/Onboarding/UseCase/View/OnboardingUseCaseSelectionScreen.swift

@@ -34,6 +34,11 @@ struct OnboardingUseCaseSelectionScreen: View {
     var titleContent: some View {
         VStack(spacing: 8) {
             Image(Asset.Images.onboardingUseCaseIcon.name)
+                .resizable()
+                .renderingMode(.template)
+                .foregroundColor(theme.colors.accent)
+                .frame(width: OnboardingMetrics.iconSize, height: OnboardingMetrics.iconSize)
+                .background(Circle().foregroundColor(.white).padding(2))
                 .padding(.bottom, 8)
                 .accessibilityHidden(true)
             
@@ -99,9 +104,9 @@ struct OnboardingUseCaseSelectionScreen: View {
                         
                         useCaseButtons
                     }
-                    .frame(maxWidth: OnboardingMetrics.maxContentWidth,
-                           maxHeight: OnboardingMetrics.maxContentHeight)
-                    .padding(16)
+                    .frame(maxWidth: OnboardingMetrics.maxContentWidth)
+                    .padding(.top, OnboardingMetrics.topPaddingToNavigationBar)
+                    .padding(.horizontal, 16)
                 }
                 .frame(maxWidth: .infinity)
                 
@@ -120,11 +125,11 @@ struct OnboardingUseCaseSelectionScreen: View {
 @available(iOS 14.0, *)
 struct OnboardingUseCase_Previews: PreviewProvider {
     static let stateRenderer = MockOnboardingUseCaseSelectionScreenState.stateRenderer
+    
     static var previews: some View {
-        NavigationView {
-            stateRenderer.screenGroup()
-                .navigationBarTitleDisplayMode(.inline)
-        }
-        .navigationViewStyle(StackNavigationViewStyle())
+        stateRenderer.screenGroup(addNavigation: true)
+            .theme(.light).preferredColorScheme(.light)
+        stateRenderer.screenGroup(addNavigation: true)
+            .theme(.dark).preferredColorScheme(.dark)
     }
 }