fix: stale RCTModalHostViewController blocks touch inputs

[mdjastrzebski]

Summary:

Resolves #54856
Resolves #50152

Fixes a but when RCTModalHostViewController tries to dismiss itself using the following code:

- (void)dismissViewController:(UIViewController *)modalViewController
                     animated:(BOOL)animated
                   completion:(void (^)(void))completion
{
  [modalViewController dismissViewControllerAnimated:animated completion:completion];
}

But since it's already presenting another VC on top of it (e.g., login web view VC, photo picker VC, etc), it dismisses that view but not itself, which results in a transparent modal VC (all the UI is unmounted) that is the top VC blocking all touch input.

The change is minimal: instead of calling dismissViewControllerAnimated:completion: on modalViewController, which has two different behaviors depending on whether that VC is presenting another VC, it calls it on modalViewController.presentingViewController, which has a unique behavior of dismissing modalViewController.

Changelog:

Test Plan:

1. Run Modal examples in the RN Tester app to confirm that this code still works ok in the base case.
2. Run the reproducer from [iOS] ModalHostViewController not properly dismissed if presenting another VC #54856 with and without the change to confirm this code fixes the issue.

[mdjastrzebski]

Danger change is failing due to non-related error: https://github.com/facebook/react-native/actions/runs/20138652296/job/57799224046

[mdjastrzebski]

This also fixes the bug mentioned in #54781:

The first is when dismissing and presenting different modals in parallel, when we do this we end up in a weird state where the second modal is not presented and seems to block the UI from receiving touches.

without introducing stacked modals or any breaking change.

[cipolleschi]

Thanks for the fix. It should be safe... but you'll never know with our internal apps and tests. 🤞

[meta-codesync]

@cipolleschi has imported this pull request. If you are a Meta employee, you can view this in D90118522.

[mdjastrzebski]

NB: The failing workflow does not seem related to the changes:

0curl: (6) Could not resolve host: central.sonatype.com

[cipolleschi]

Some internal comments from @javache :

This should already be equivalent

If you call this method on the presented view controller itself, UIKit asks the presenting view controller to handle the dismissal.
https://developer.apple.com/documentation/uikit/uiviewcontroller/dismiss(animated:completion:)

---

Can we have a reproducer for this in RNTester?
It's very easy for this to cause other regressions. Really, dismissing a modal that's currently presenting another modal is not something we should be doing anyway.

[lodev09]

@cipolleschi IOS supports undimmed sheets. It's very possible to have a use-case where user will dismiss the modal when there's a UISheetPresentationController presented. Here's a duplicate PR I did for this issue #55005