fix(iOS): activityState regression check false-positive (#2404)

## Description

We had an issue introduced in #2389 that added the preload. We
temporarily
have an assumption in native stack, that the `activityState` can only
progress when
`Screen` component is rendered (directly) inside native stack navigator.
This invariant
was enforced with appropriate checks on native side. It turns out that
we were wrong in our
way of checking whether the `Screen` belongs to native stack or not - we
have forgotten about
`RNSContainerNavigationController` class that is used when rendering
`ScreenContainer` with `hasTwoStates: true`
and which inherits from `RNSNavigationController`.

## Changes

~Added a `isNativeStackViewController` method to
`RNSNavigationController` and overrode it in subclass.~

Added `RNSScreenView#isNativeStackScreen` method, which checks whether
our direct react superview is a `RNSScreenStackView`.

I've found checking for `_controller.navigationController` not reliable,
as `navigationController` can be found arbitrarily high in the view
hierarchy.

## Test code and steps to reproduce

Reported by Expo. If you want to reproduce this: create a JS stack
navigator with bottom tabs inside (with `hasTwoStates: true`),
and then a regular JS stack inside & try to navigate to any screen. 

We have not caught that earlier, because we're not testing regular JS
stack at all.

## Checklist

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

ios/RNSScreen.mm

@@ -307,15 +307,25 @@ - (void)setActivityStateOrNil:(NSNumber *)activityStateOrNil
 {
   int activityState = [activityStateOrNil intValue];
   if (activityStateOrNil != nil && activityState != -1 && activityState != _activityState) {
-    if ([_controller.navigationController isKindOfClass:RNSNavigationController.class] &&
-        _activityState < activityState) {
-      RCTLogError(@"[RNScreens] activityState can only progress in NativeStack");
-    }
+    [self maybeAssertActivityStateProgressionOldValue:_activityState newValue:activityState];
     _activityState = activityState;
     [_reactSuperview markChildUpdated];
   }
 }
 
+- (void)maybeAssertActivityStateProgressionOldValue:(int)oldValue newValue:(int)newValue
+{
+  if (self.isNativeStackScreen && newValue < oldValue) {
+    RCTLogError(@"[RNScreens] activityState can only progress in NativeStack");
+  }
+}
+
+/// Note that this method works only after the screen is actually mounted under a screen stack view.
+- (BOOL)isNativeStackScreen
+{
+  return [_reactSuperview isKindOfClass:RNSScreenStackView.class];
+}
+
 #if !TARGET_OS_TV && !TARGET_OS_VISION
 - (void)setStatusBarStyle:(RNSStatusBarStyle)statusBarStyle
 {

ios/RNSScreenStack.mm

@@ -953,7 +953,7 @@ - (void)navigationController:(UINavigationController *)navigationController
 
 - (void)markChildUpdated
 {
-  // do nothing
+  // In native stack this should be called only for `preload` purposes.
   [self updateContainer];
 }