Fix ScrollView recycled content inset (#57494)

Summary:
Fixes #57314.

When a Fabric `ScrollView` is recycled on iOS, `prepareForRecycle` resets native scroll state before the view is reused. `contentInset` was being reset to `UIEdgeInsetsZero`, which prevents stale native insets from leaking between recycled views, but also drops a valid non-zero `contentInset` from the current props.

If the recycled view is mounted again with the same `contentInset` prop value, `updateProps` may not reapply it because the props did not change. This can leave the native `UIScrollView` with `contentInset = 0` even though React props still specify a non-zero inset.

This change keeps the stale-state protection, but resets `contentInset` back to the value from the current props instead of always zeroing it.

## Changelog:

[IOS] [FIXED] - Preserve Fabric ScrollView contentInset when recycling iOS native views

Pull Request resolved: #57494

Test Plan:
Verified with the repro from #57314:

1. Cloned and installed `gimi-anders/rn-contentinset-recycle-repro`
2. Ran the app with the existing implementation and reproduced the issue:
   - Step 0: first ScrollView reports `native contentInset.top = 200`
   - Step 1: first ScrollView is unmounted
   - Step 2: recycled ScrollView reports `native contentInset.top = 0`
3. Applied this change to the repro app’s local React Native source and rebuilt with React Native Core built from source.
4. Re-ran the repro:
   - Step 2 now reports `native contentInset.top = 200`

Also verified that the previous stale-inset protection is preserved: `prepareForRecycle` still overwrites the recycled native `UIScrollView.contentInset`; it now overwrites it with the current props value instead of always using `UIEdgeInsetsZero`.

| Before | After |
| --- | --- |
| https://github.com/user-attachments/assets/e69ce800-23ab-4406-8700-f57511af85d8 | https://github.com/user-attachments/assets/35b93cff-0804-455c-a85c-2c0b05d35417 |

Reviewed By: cipolleschi

Differential Revision: D111262993

Pulled By: javache

fbshipit-source-id: a98729d105792c51a7dec6eee8510cfd086e372e

Author: adamivancza

packages/react-native/React/Fabric/Mounting/ComponentViews/ScrollView/RCTScrollViewComponentView.mm

@@ -696,8 +696,7 @@ - (void)prepareForRecycle
   // Invalidate cached content size so that updateState: recalculates the
   // container frame after zoomScale reset (which may have mutated it in RTL).
   _contentSize = CGSizeZero;
-  // Reset contentInset to prevent stale insets leaking into recycled scroll views.
-  _scrollView.contentInset = UIEdgeInsetsZero;
+  _scrollView.contentInset = RCTUIEdgeInsetsFromEdgeInsets(props.contentInset);
   // We set the default behavior to "never" so that iOS
   // doesn't do weird things to UIScrollView insets automatically
   // and keeps it as an opt-in behavior.