fix: setting headerBackTitleVisible to false not working on iOS

[zetavg]

Motivation

According to the docs, setting headerBackTitleVisible to false should hide the back title on iOS, while this is not the case with react-native-screens v3.29+.

Cause

With the current code, backTitle={headerBackTitleVisible ? headerBackTitle : ' '}, the back title is set to a blank string if headerBackTitleVisible is false. However, in newer versions of react-native-screens, the backTitle will be considered blank if it only contains white spaces, making it fallback to the default title - which makes the back title not hidden at all.

Fix

Assign the backTitleVisible property of RNSScreenStackHeaderConfig native component, which seems to be a legit way to hide the back title.

Test plan

1. Create a native stack navigator with the backTitleVisible screen option set to false.
2. See if the back title is hidden on iOS when navigating to another screen.

Expected	Not Expected

• May need to test if assigning the new property will break older versions of react-native-screens.
  • Tested with react-native-screens 3.20.0 and 3.21.0, app does not crash and the back title remains hidden-able.

[github-actions]

Hey @zetavg! Thanks for opening your first pull request in this repo. If you haven't already, make sure to read our contribution guidelines.

[netlify]

✅ Deploy Preview for react-navigation-example ready!

Name	Link
🔨 Latest commit	2573816
🔍 Latest deploy log	https://app.netlify.com/sites/react-navigation-example/deploys/6641d37941fbc800087616dc
😎 Deploy Preview	https://deploy-preview-11937--react-navigation-example.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 33.33333% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 77.00%. Comparing base (d90ed76) to head (84cca6c).
Report is 2 commits behind head on main.

Files	Patch %	Lines
packages/native-stack/src/views/HeaderConfig.tsx	33.33%	1 Missing and 1 partial ⚠️

❗ Your organization needs to install the Codecov GitHub app to enable full functionality.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11937      +/-   ##
==========================================
- Coverage   77.03%   77.00%   -0.03%     
==========================================
  Files         210      210              
  Lines        6339     6341       +2     
  Branches     2506     2508       +2     
==========================================
  Hits         4883     4883              
- Misses       1402     1403       +1     
- Partials       54       55       +1     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.