chore: throw error when failed to find fragment for react root view

[kkafar]

Description

Changes introduced in #1553 in case of FragmentManager.findFragment method throwing an exception could lead to some hard to debug behaviour. Now in case something goes wrong, we will get clear error message.

Changes

Code responsible for resolving FragmentManager when React Native is loaded of fragment now throws uncaught exception.

Test code and steps to reproduce

See #1553 and #1506

Checklist

• Included code example that can be used to test this change
• Updated TS types
• Updated documentation:
  • https://github.com/software-mansion/react-native-screens/blob/main/guides/GUIDE_FOR_LIBRARY_AUTHORS.md
  • https://github.com/software-mansion/react-native-screens/blob/main/native-stack/README.md
  • https://github.com/software-mansion/react-native-screens/blob/main/src/types.tsx
  • https://github.com/software-mansion/react-native-screens/blob/main/src/native-stack/types.tsx
• Ensured that CI passes