Avoid running side-effects in didMoveToWin after invalidation (#700)

## Description

This PR resolves an issue on iOS where we'd run a side-effect code in didMoveToWindow after the view has been invalidated (that is removed from the react-native tree). As a result we'd end up getting the following crash:

```
UIViewControllerHierarchyInconsistency child view controller:<UINavigationController: 0xREDACTED should have parent view controller:<RNSScreen: 0xREDACTED but requested parent is:<UINavigationController: 0xREDACTED>
```

The problem turned out to be related to the fact we've been attempting to reattach view to a different view controller than the one it's been previously attached to. However, the code that attaches it should not be run in the first place as the view has already been removed. After investigating it turned out that layout animations sometimes cause didMoveToWindow run despite the fact the view has been removed from the hierarchy. In this PR we add an extra check to avoid running side-effects from that callback when the view is invalidated.

## Changes

We change didMoveToWindow logic in both RNSScreenStack and RNSScreenContainer such that we only run side-effect when the view has not been invalidated. To check that we add a marker _invalidated that is set in invalidate callback.


## Test code and steps to reproduce

The below app can be used to reproduce the crash. Before this change the app would crash after pressing the button "move" twice. After this change the app no longer crashes.

```js
import React, { Component, useState } from 'react';
import {
  StyleSheet,
  Button,
  View,
  Text,
  LayoutAnimation,
} from 'react-native';
import {
  Screen,
  ScreenStack,
  ScreenStackHeaderConfig,
  ScreenContainer,
  enableScreens,
} from 'react-native-screens';

enableScreens(true);

function Step({ move, title, color }) {
  return (
    <View style={[styles.view, { backgroundColor: color }]}>
      <Button title="Move" onPress={move} />
    </View>
  );
}

function App() {
  const [state, setState] = useState(0);

  if (state === 2) return <Step move={() => setState(0)} color="green" />;
  return (
    <ScreenStack style={styles.container} key={state < 2 ? 'one' : 'two'}>
      <Screen stackPresentation="containedModal" style={styles.container}>
        <ScreenStack style={styles.container}>
          <Screen style={styles.container} stackPresentation="containedModal">
            <ScreenStack style={styles.container}>
              <Screen style={styles.container}>
                <ScreenStackHeaderConfig title={'One'} />
                <Step move={() => setState(1)} color="pink" />
              </Screen>
            </ScreenStack>
          </Screen>
        </ScreenStack>
      </Screen>
      {state === 1 && (
        <Screen
          style={styles.container}
          stackPresentation="containedModal"
          stackAnimation="fade">
          <ScreenStack style={styles.container}>
            <Screen style={styles.container}>
              <Step
                move={() => {
                  LayoutAnimation.configureNext(LayoutAnimation.Presets.linear);
                  setState(2);
                }}
                color="blue"
              />
            </Screen>
          </ScreenStack>
        </Screen>
      )}
    </ScreenStack>
  );
}

const styles = StyleSheet.create({
  container: {
    ...StyleSheet.absoluteFillObject,
  },
  view: {
    paddingTop: 100,
    ...StyleSheet.absoluteFillObject,
  },
});

export default App;

```

Author: kmagiera

ios/RNSScreenContainer.m

@@ -53,6 +53,7 @@ - (UIViewController *)findActiveChildVC
 
 @implementation RNSScreenContainerView {
   BOOL _needUpdate;
+  BOOL _invalidated;
   __weak RNSScreenContainerManager *_manager;
 }
 
@@ -63,6 +64,7 @@ - (instancetype)initWithManager:(RNSScreenContainerManager *)manager
     _reactSubviews = [NSMutableArray new];
     _controller = [[RNScreensViewController alloc] init];
     _needUpdate = NO;
+    _invalidated = NO;
     _manager = manager;
     [self addSubview:_controller.view];
   }
@@ -216,13 +218,17 @@ - (void)didUpdateReactSubviews
 
 - (void)didMoveToWindow
 {
-  if (self.window) {
+  if (self.window && !_invalidated) {
+    // We check whether the view has been invalidated before running side-effects in didMoveToWindow
+    // This is needed because when LayoutAnimations are used it is possible for view to be re-attached
+    // to a window despite the fact it has been removed from the React Native view hierarchy.
     [self reactAddControllerToClosestParent:_controller];
   }
 }
 
 - (void)invalidate
 {
+  _invalidated = YES;
   [_controller willMoveToParentViewController:nil];
   [_controller removeFromParentViewController];
 }

ios/RNSScreenStack.m

@@ -45,12 +45,14 @@ @implementation RNSScreenStackView {
   NSMutableArray<RNSScreenView *> *_reactSubviews;
   __weak RNSScreenStackManager *_manager;
   BOOL _hasLayout;
+  BOOL _invalidated;
 }
 
 - (instancetype)initWithManager:(RNSScreenStackManager*)manager
 {
   if (self = [super init]) {
     _hasLayout = NO;
+    _invalidated = NO;
     _manager = manager;
     _reactSubviews = [NSMutableArray new];
     _presentedModals = [NSMutableArray new];
@@ -189,7 +191,12 @@ - (void)didUpdateReactSubviews
 - (void)didMoveToWindow
 {
   [super didMoveToWindow];
-  [self maybeAddToParentAndUpdateContainer];
+  if (!_invalidated) {
+    // We check whether the view has been invalidated before running side-effects in didMoveToWindow
+    // This is needed because when LayoutAnimations are used it is possible for view to be re-attached
+    // to a window despite the fact it has been removed from the React Native view hierarchy.
+    [self maybeAddToParentAndUpdateContainer];
+  }
 }
 
 - (void)maybeAddToParentAndUpdateContainer
@@ -473,6 +480,7 @@ - (void)layoutSubviews
 
 - (void)invalidate
 {
+  _invalidated = YES;
   for (UIViewController *controller in _presentedModals) {
     [controller dismissViewControllerAnimated:NO completion:nil];
   }