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.

UnitTests/Sources/QRCodeLoginScreenViewModelTests.swift

@@ -53,7 +53,7 @@ final class QRCodeLoginScreenViewModelTests: XCTestCase {
         try await deferred.fulfill()
         XCTAssertTrue(appMediatorMock.requestAuthorizationIfNeededCalled)
         
-        context.send(viewAction: .openSettings)
+        context.send(viewAction: .errorAction(.openSettings))
         await Task.yield()
         XCTAssertTrue(appMediatorMock.openAppSettingsCalled)
         XCTAssertNil(context.qrResult)