Fix ScrollView touch events ignored in contentInset area on iOS

[cbrevik]

Summary:

Fixes #54123

In RN 0.80, betterHitTest:withEvent: in RCTScrollViewComponentView was added, which returns self (the RCTScrollViewComponentView wrapper view) when a touch point falls inside the scroll view's bounds. This causes touches in the contentInset area — where no content is rendered — to be absorbed by the wrapper rather than forwarded to the underlying UIScrollView, making scroll gestures in that region completely non-functional.

The fix returns _scrollView instead of self, so hit-tested touches are correctly attributed to the UIScrollView and scrolling works throughout the full bounds, including the inset area.

Changelog:

[IOS] [FIXED] - Fix ScrollView touch events ignored in contentInset area on Fabric

Test Plan:

Couldn't use the snack-repro from #54123 since this requires a native change. But using the ScrollViewSimpleExample from the RNTester, and removing a lot of the items demonstrates the behaviour change.

The two videos show attempted dragging from the region below the ScrollView content.

Before: Dragging in the inset area does nothing — scroll view does not respond

Before-fix.mov

After: Dragging in the inset area scrolls the content correctly

After-fix.mov

[meta-codesync]

@javache has imported this pull request. If you are a Meta employee, you can view this in D104644045.

[react-native-bot]

This pull request was successfully merged by @cbrevik in efcab20

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[meta-codesync]

@javache merged this pull request in efcab20.