feat: Add accessibility collection support to VirtualizedList

[nathannewyen]

Summary

This PR adds accessibility collection support to VirtualizedList, enabling Android TalkBack to announce "item X of Y" when navigating through list items.

Closes #30975

Changes

• VirtualizedListProps.js: Added AccessibilityCollectionItem type and included it in ListRenderItemInfo
• VirtualizedList.js:
  • Computes accessibilityCollectionItem for each cell in _pushCells()
  • Adds accessibilityCollection (rowCount/columnCount) to ScrollView wrapper
• VirtualizedListCellRenderer.js: Receives and applies accessibilityCollectionItem prop to cell View and passes it to renderItem callback
• ViewAccessibility.js: Added Flow types for AccessibilityCollection and AccessibilityCollectionItem to AccessibilityPropsAndroid
• FlatList.js: Fixed multi-column grid accessibility by computing proper row/column indices

Changelog:

[ANDROID] [ADDED] - Added accessibility collection support to VirtualizedList for TalkBack "item X of Y" announcements

Test Plan

• All existing VirtualizedList tests pass (74 passed, 2 skipped)
• All existing FlatList tests pass (12 passed)
• Flow type check passes (0 errors)
• ESLint passes

To test with TalkBack:

1. Enable TalkBack on Android device
2. Navigate through a FlatList/VirtualizedList
3. TalkBack should announce "item X of Y" for each item

🤖 Generated with Claude Code

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