fix(iOS, Stack): Fix calculating insets for header title

[t0maboro]

Description

This PR is changing the approach for calculating edge insets of the navigation bar.
On iOS 26, the hierarchy has changed significantly, resulting in placing too long header content, which might be covered by the right button.

Old hierarchy:

Class: UINavigationBar | Frame: {{0, 56.333333333333343}, {440, 44}} | Margins => top: 13.67, leading: 8.00, bottom: 8.00, trailing: 8.00
  Class: _UINavigationBarContentView | Frame: {{0, 0}, {440, 44}} | Margins => top: 5.67, leading: 20.00, bottom: 0.00, trailing: 20.00
    ...
    Class: _UINavigationBarTitleControl | Frame: {{66, 13.666666666666664}, {268, 17}} | Margins => top: 8.00, leading: 8.00, bottom: 8.00, trailing: 8.00

New hierarchy:

Class: UINavigationBar | Frame: {{0, 56.333333333333343}, {440, 54}} | Margins => top: 5.67, leading: 20.00, bottom: 0.00, trailing: 20.00
  Class: UIKit.NavigationBarContentView | Frame: {{0, 0}, {440, 54}} | Margins => top: 5.67, leading: 0.00, bottom: 0.00, trailing: 0.00
    Class: UIKit.NavigationBarTransitionContainer | Frame: {{0, 0}, {440, 54}} | Margins => top: 8.00, leading: 8.00, bottom: 8.00, trailing: 8.00
      Class: _UINavigationBarHostedViewContainer | Frame: {{0, 0}, {440, 54}} | Margins => top: 8.00, leading: 8.00, bottom: 8.00, trailing: 8.00
        Class: _UINavigationBarHostedViewWrapper | Frame: {{80, 13.5}, {240, 17}} | Margins => top: 8.00, leading: 8.00, bottom: 8.00, trailing: 8.00
          Class: _UINavigationBarTitleControl | Frame: {{0, 0}, {240, 17}} | Margins => top: 8.00, leading: 8.00, bottom: 8.00, trailing: 8.00

In the new approach, I'm summing up all directionalLayoutMargins between _UINavigationBarTitleControl and NavigationBarContentView. I know that this approach doesn't seem to be super-solid, but somehow I need to traverse the structure to get _UINavigationBarTitleControl and calculate cumulative layout properly.

Changes

• Extended UINavigationBar with the new method for calculating the insets between the content and title views.

Screenshots / GIFs

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Before

After

Test code and steps to reproduce

TestHeaderTitle example on iOS 26 and 18.

Checklist

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

[kkafar]

It looks like they're using SwiftUI to implement UIKit xD

[kkafar]

Few comments & questions

[kkafar]

On the snippet you provided in PR description I can observe, that titleControl has non-zero insets. Why do we skip them by starting from superview?

[t0maboro]

I'm following the same approach as for the < iOS26 implementation for which we stopped at _UINavigationBarTitleControl level

[kkafar]

This loop also does not include insets of UINavigationBar itself, is it intentional?

[t0maboro]

NavigationBar was left in their old calculation method: https://github.com/software-mansion/react-native-screens/blob/main/ios/RNSScreenStackHeaderConfig.mm#L256. For this change, I intentionally wanted to calculate everything in between UINavigationBar and title control view.

[t0maboro]

This PR introduces a regression with shrinking title component in landscape mode too much. I'm working on another approach for calculating edge insets. Closing this in favor of: #3210