fix(iOS): activityState regression check false-positive

[kkafar]

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
• Ensured that CI passes

[maciekstosio]

LGTM 🎉