Minimize the virtualized-lists fork

[Saadnajmi]

Summary

• sync @react-native-macos/virtualized-lists implementation and tests with the React Native merge-base
• retain one macOS-only delta for native vertical inversion so trackpad, mouse-wheel, and scrollbar behavior remain native
• keep horizontal inverted lists transform-based
• move opt-in keyboard selection state, callbacks, isSelected, and selectRowAtIndex into FlatList
• keep ScrollView generic; it only preserves native children when macOS native inversion is active

Why

The fork duplicated upstream list implementation primarily for keyboard selection and native inversion. Selection is FlatList/listbox semantics, while VirtualizedList should remain generic virtualization infrastructure. Native vertical inversion still needs a minimal strategy clause because upstream transform inversion does not provide correct macOS scrolling interactions.

After this change, the virtualized-lists fork differs from the upstream merge-base in only Lists/VirtualizedList.js, where vertical macOS inversion omits transform styles.

Behavior notes

• FlatList keeps the existing macOS keyboard-selection API.
• SectionList and direct VirtualizedList no longer expose the unused keyboard-selection API.
• Vertical inverted lists continue using native macOS inversion.
• Horizontal inverted lists use scaleX(-1) because AppKit native inversion is vertical only.

Validation

• yarn flow-check
• 11 focused Jest suites: 189 passed, 2 skipped, 82 snapshots
• Prettier and ESLint on all changed source files
• verified the virtualized-lists package has exactly one implementation-file delta from upstream