fixup! Convert ConfirmationView form UIKit to SwiftUI

This PR is experimental, yet important first step towards transitioning
to SwiftUI. ConfirmationView has been rewritten entirely in SwiftUI. The
primary motivator for this PR was the frustrating nature of UIKit constraints.

Key factors to keep in mind while reviewing:

1. Checkmark image has been made smaller, which was the request from the
design team

2. UIFont does not translate 1:1 to SwiftUI Font, meaning the same font
looks just a little big different now. But dynamic scaling works, and all
our default fonts translate to expected outcome (font size, weight etc.)

3. Some approaches used in view layouts is due to the restrictions of
SwiftUI 1.0 capabilities. Those can and will be upgraded in the future

4. The naming of Views, and Objects, as well as file locations in the
directory are up for discussion. Everyone's input is much appreciated.

5. Prefix SwiftUI is used in lots of places due to a conflict with existing
custom objects Button and Image

6. New HeaderSwiftUI view does not include all the possible configuration
possibilities, as confirmations view's needs are not very demanding. So,
that view can be upgraded in future.

This PR also covers the ticket MOB-2488 which focuses on ADA-compliance
in ConfigurationsView

SnapshotTests/SecureConversationsConfirmationScreenLayoutTests.swift

@@ -20,7 +20,7 @@ class SecureConversationsConfirmationScreenLayoutTests: SnapshotTestCase {
 
         assertSnapshot(
             matching: viewController,
-            as: .image(on: .iPhone8(.landscape)),
+            as: .image,
             named: self.nameForDevice()
         )
     }