fix(Android): crash API 25 when going back from screen with flat list (software-mansion#2964)

## Description

Fixes software-mansion#2810

This PR should fix a crash when going back from the screen that has flat
list.

## Changes
 There are two exceptions thrown:

**First:**
```
Error: Exception in HostFunction: android.view.ViewRootImpl$CalledFromWrongThreadException: Only the original thread that created a view hierarchy can touch its views.
```

**Second:**
```
java.lang.IndexOutOfBoundsException: getChildDrawingOrder() returned invalid index 1 (child count is 1)
```

And it fails around this place in `Screen.kt`:

```
(...)
                if (parent is SwipeRefreshLayout && child is ImageView) {
                    // SwipeRefreshLayout class which has CircleImageView as a child,
                    // does not handle `startViewTransition` properly.
                    // It has a custom `getChildDrawingOrder` method which returns
                    // wrong index if we called `startViewTransition` on the views on new arch.
                    // We add a simple View to bump the number of children to make it work.
                    // TODO: find a better way to handle this scenario
                        it.addView(View(context), i)
                } else {
                    child?.let { view -> it.startViewTransition(view) }
                }
(...)
```

Based on the comment, I assume `it.addView(View(context), i)` is to
prevent the **second** crash. Because the **first** exception, we do not
add "workaround" view, thus we run into **second**. We get the **first**
exception, as the operation is performed from different thread, thus I
ensure the adding view is performed from UIThread.

## Test code and steps to reproduce

<details>
<summary>Source code</summary>

```
import * as React from 'react';
import { View, Text, FlatList } from 'react-native';
import { NavigationContainer, useNavigation } from '@react-navigation/native';
import { createNativeStackNavigator, NativeStackScreenProps } from '@react-navigation/native-stack';
import { Button } from '@react-navigation/elements';
import { SafeAreaProvider } from 'react-native-safe-area-context';

type StackParamList = {
  Home: undefined;
  Details: undefined;
};

function HomeScreen() {
  const navigation = useNavigation<NativeStackScreenProps<StackParamList, 'Home'>['navigation']>();

  return (
    <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
      <Text>Home Screen</Text>
      <Button onPress={() => navigation.navigate('Details')}>
        Go to Details
      </Button>
    </View>
  );
}

function DetailsScreen() {
  const [isRefreshing, setIsRefreshing] = React.useState(false);

  return (
    <View style={{ flex: 1, alignItems: 'center', justifyContent: 'center' }}>
      <FlatList
        data={[1, 2, 3, 4, 5]}
        renderItem={({ item }) => <Text>{item}</Text>}
        onRefresh={() => {
          return new Promise<void>((resolve) => {
            setIsRefreshing(true);
            setTimeout(() => {
              resolve();
            }, 3000);
          }).then(() => {
            setIsRefreshing(false);
          });
        }}
        refreshing={isRefreshing}
      />
    </View>
  );
}

const Stack = createNativeStackNavigator<StackParamList>();

function NestedStack() {
  return (
    <Stack.Navigator>
      <Stack.Screen name="Home" component={HomeScreen} />
      <Stack.Screen name="Details" component={DetailsScreen} />
    </Stack.Navigator>
  );
}

export default function App() {
  return (
    <SafeAreaProvider>
      <NavigationContainer>
        <NestedStack />
      </NavigationContainer>
    </SafeAreaProvider>
  );
};
```

</details>

## Checklist

- [x] Included code example that can be used to test this change
- [ ] Ensured that CI passes

---------

Co-authored-by: Kacper Kafara <[email protected]>

Author: 2 people

android/src/fabric/java/com/swmansion/rnscreens/NativeProxy.kt

@@ -59,7 +59,13 @@ class NativeProxy {
 
         val screen = weakScreeRef.get()
         if (screen is Screen) {
-            screen.startRemovalTransition()
+            val isScheduled =
+                screen.post {
+                    screen.startRemovalTransition()
+                }
+            if (!isScheduled) {
+                Log.w("[RNScreens]", "Failed to schedule removal transition start for screen with tag $screenTag")
+            }
         } else {
             Log.w("[RNScreens]", "Reference stored in NativeProxy for tag $screenTag no longer points to valid object.")
         }