feat: [IOPID-1391] Fix tablet compatibility alert displaying (#5417)

## Short description
This PR fixes the continuously displaying of the Tablet compatibility
alert during the login flow. It took the chance to refactor the
`LandingScreen` from `PureComponent` to `FunctionComponent`.

<details open><summary>Details</summary>
<p>

| ❌ | ✅ |
| - | - |
| <video
src="https://github.com/pagopa/io-app/assets/16268789/68836f13-88f9-41a5-98a6-eceea56de750"
/> | <video
src="https://github.com/pagopa/io-app/assets/16268789/0e6e24ff-31a2-4aef-958e-0402564629e6"
/> |

</p>

</details> 

## How to test
Launch the app on an Android Tablet and check that the Alert is shown
only at every first render of `LandingScreen`.

ts/navigation/AuthenticationNavigator.tsx

@@ -10,7 +10,7 @@ import CiePinScreen from "../screens/authentication/cie/CiePinScreen";
 import CieWrongCiePinScreen from "../screens/authentication/cie/CieWrongCiePinScreen";
 import IdpLoginScreen from "../screens/authentication/IdpLoginScreen";
 import IdpSelectionScreen from "../screens/authentication/IdpSelectionScreen";
-import LandingScreen from "../screens/authentication/LandingScreen";
+import { LandingScreen } from "../screens/authentication/LandingScreen";
 import TestAuthenticationScreen from "../screens/authentication/TestAuthenticationScreen";
 import MarkdownScreen from "../screens/development/MarkdownScreen";
 import { AuthSessionPage } from "../screens/authentication/idpAuthSessionHandler";