fix: handle React Native loaded on Fragment

[kkafar]

Description

Fixes #1506

ScreenContainer#setupFragmentManager method resolves FragmentManager instance for ScreenContainer to use for conducting transactions. Until now, when first (not nested) ScreenContainer was initialised we took FragmentManager from top level activity, but it leads to conflicts with native Android navigation when React Native is not loaded directly in main activity (there are cases (see #1506) when both react-native-screens & Android native navigation use simultaneously the same FragmentManager leading to crashes).

Changes

Added a method resolving fragment manager whose fragment's view is ReactRootView.

Test code and steps to reproduce

See #1506 for crash description and how to reproduce.

Checklist

• Included code example that can be used to test this change
• Ensured that CI passes

[kkafar]

See the comment below

[kkafar]

Potentially we could catch the exception here and fallback to context.supportFragmentManager:

Suggested change

	// We are in some custom setup & we want to use the closest fragment manager in hierarchy.
	// `findFragment` method throws IllegalStateException when it fails to resolve appropriate
	// fragment. It might happen when e.g. React Native is loaded directly in Activity
	// but some custom fragments are still used. However such use case seems highly unlikely
	// so, as for now, we let application crash.
	FragmentManager.findFragment<Fragment>(rootView).childFragmentManager
	// We are in some custom setup & we want to use the closest fragment manager in hierarchy.
	// `findFragment` method throws IllegalStateException when it fails to resolve appropriate
	// fragment. It might happen when e.g. React Native is loaded directly in Activity
	// but some custom fragments are still used. However such use case seems highly unlikely
	// so, as for now, we let application crash.
	try {
	FragmentManager.findFragment<Fragment>(rootView).childFragmentManager
	} catch (IllegalStateException e) {
	context.supportFragmentManager
	}

[kkafar]

Change added with 714ddea