chore: Prevent setting RTL mode in test examples (#2130)

## Description

This PR is a follow-up to #2084 that fixes setting incorrect RTL mode in
our example apps.
The reason why it is being forced is that `I18nManager.forceRTL(true)`
is being called from the global scope, which causes to force RTL, even
if we're only importing the component **from file**.

## Changes

- Moved `I18nManager.forceRTL(true);` to inner scope of App components.

## Test code and steps to reproduce

Just run TestsExample & FabricTestExample ¯\_(ツ)_/¯

## Checklist

- [X] Ensured that CI passes

FabricTestExample/src/Test654.js

@@ -5,9 +5,15 @@ import { createNativeStackNavigator } from '@react-navigation/native-stack';
 
 const Stack = createNativeStackNavigator();
 
-I18nManager.forceRTL(true);
-
 export default function App() {
+  React.useEffect(() => {
+    I18nManager.forceRTL(true);
+
+    return () => {
+      I18nManager.forceRTL(false);
+    };
+  }, []);
+
   return (
     <NavigationContainer>
       <Stack.Navigator>

FabricTestExample/src/Test831.tsx

@@ -12,9 +12,15 @@ type Props = {
 
 const Stack = createNativeStackNavigator();
 
-I18nManager.forceRTL(true);
-
 export default function App(): JSX.Element {
+  React.useEffect(() => {
+    I18nManager.forceRTL(true);
+
+    return () => {
+      I18nManager.forceRTL(false);
+    };
+  }, []);
+
   return (
     <NavigationContainer>
       <Stack.Navigator screenOptions={{ headerShown: false }}>

TestsExample/src/Test654.js

@@ -5,9 +5,15 @@ import { createNativeStackNavigator } from '@react-navigation/native-stack';
 
 const Stack = createNativeStackNavigator();
 
-I18nManager.forceRTL(true);
-
 export default function App() {
+  React.useEffect(() => {
+    I18nManager.forceRTL(true);
+
+    return () => {
+      I18nManager.forceRTL(false);
+    };
+  }, []);
+
   return (
     <NavigationContainer>
       <Stack.Navigator>

TestsExample/src/Test831.tsx

@@ -12,9 +12,15 @@ type Props = {
 
 const Stack = createNativeStackNavigator();
 
-I18nManager.forceRTL(true);
-
 export default function App(): JSX.Element {
+  React.useEffect(() => {
+    I18nManager.forceRTL(true);
+
+    return () => {
+      I18nManager.forceRTL(false);
+    };
+  }, []);
+
   return (
     <NavigationContainer>
       <Stack.Navigator screenOptions={{ headerShown: false }}>