feat: Add defaultValue prop to search bar

[rrebase]

Description

Add defaultValue prop to search bar, enabling initial text value configuration.

useLayoutEffect(() => {
  navigation.setOptions({
    headerSearchBarOptions: {
      defaultValue: 'Some default value',
    },
  });
}, [navigation]);

A common use-case for a default value is deep linking to a search screen that makes use of the search bar.

It's possible to imperatively set the value via ref using setText, however there's no the suitable callback to do it reliably without seeing the initial empty value / flickering.

Named the prop defaultValue to be consistent with RN TextInput where it's also used for the initial value for uncontrolled TextInput component.

While it works well for my use case, I'm not fully sure if adding a defaultValue is the best approach with the imperative nature / paradigm how react-native-screens defines the search bar, maybe there's obvious downsides that I'm missing, would love to hear your thoughts.

• Resolves Set the default value of search bar? #1617
• Resolves Expo - Unable to set default text for header search bar using ref #2392

Test code and steps to reproduce

Tested in my app with a patch with these changes on:

• iOS (paper)
• Android (paper)

I tried to run the react-native-screens example app, but got 'No component found for view with name "RNScreenStackHeaderConfig" on iOS after following the Working on iOS steps and didn't have time to debug it atm. Also the steps mention yarn prepare in react-navigation, but there's no such script.

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