[iOS] Make scrollToEnd include adjusted content inset

[eliotgevers]

Summary:

Fixes #57522.

ScrollView.scrollToEnd() currently computes its iOS Fabric endpoint from UIScrollView.contentInset. When UIKit supplies safe-area or bar adjustments through adjustedContentInset, the command stops before the same endpoint a user can reach by dragging.

This change uses adjustedContentInset when constructing the vertical or horizontal end target. It also adds a focused native regression test with a 100-point viewport, 200-point content height, zero raw inset, and a 20-point adjusted bottom inset. scrollToEnd() must finish at offset 120.

This is related to, but distinct from, #56189. That PR moves general scrollTo clamping into scrollToOffset and uses adjustedContentInset; however, scrollToEnd() still constructs an already-valid but too-small target from raw contentInset, so the later clamp does not increase it.

The public reproduction starts from the official React Native reproducer template and does not use Expo, navigation, a keyboard, or an explicit contentInset:

https://github.com/eliotgevers/react-native-scroll-to-end-adjusted-inset-repro

Changelog:

[IOS] [FIXED] - Make ScrollView.scrollToEnd() include system-adjusted content insets

Test Plan:

Tested on an iPhone 17 Pro Max simulator running iOS 26.5 with React Native compiled from source.

Native implementation	scrollToEnd()	scrollTo({y: 9999})	Manual end
Stock React Native 0.86.0	364	364	398
#56189 effective Fabric logic	364	398	398
#56189 logic plus this change	398	398	398

The 34-point difference equals the simulator's adjusted bottom safe-area inset.

Stock React Native 0.86.0	Patched native source

Focused RNTester regression test:

Test Suite 'RCTScrollViewComponentViewTests' passed.
Executed 1 test, with 0 failures in 0.034 seconds.
** TEST SUCCEEDED **

The test was run through RNTesterPods.xcworkspace, scheme RNTester, with:

xcodebuild test \
  -workspace RNTesterPods.xcworkspace \
  -scheme RNTester \
  -sdk iphonesimulator \
  -destination 'platform=iOS Simulator,id=<simulator-id>' \
  -only-testing:RNTesterUnitTests/RCTScrollViewComponentViewTests

Local RNTester harness note

Current main locally hit an unrelated compile error in RCTTurboModuleArrayBufferTests.mm (detail::OwnedBytesBuffer is not declared by that file's imports). I temporarily excluded that existing test source from the local focused build so this new test could compile and run. That exclusion is not included in this PR.

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