General tidy-up related to QR codes. (#4865)

* Tidy-up Rust to Swift mapping.

* Refactor out a dedicated QRCodeErrorView.

* Use the new QRCodeErrorView for most error state snapshots.

* Simplify QRCodeErrorView structure.

Also updates the background to match the designs.

* Fix a small compile error in the unit tests.

AccessibilityTests/Sources/GeneratedAccessibilityTests.swift

@@ -419,6 +419,10 @@ extension AccessibilityTests {
         try await performAccessibilityAudit(named: "PollView_Previews")
     }
 
+    func testQRCodeErrorView() async throws {
+        try await performAccessibilityAudit(named: "QRCodeErrorView_Previews")
+    }
+
     func testQRCodeLoginScreen() async throws {
         try await performAccessibilityAudit(named: "QRCodeLoginScreen_Previews")
     }