feat: Add accessibility collection support to VirtualizedList

[saisreelasyaappali]

This enables Android TalkBack to announce "item X of Y" when navigating through VirtualizedList/FlatList items.

Changes:

• Add AccessibilityCollectionItem type to VirtualizedListProps
• Compute and pass accessibilityCollectionItem to each cell in VirtualizedList
• Apply accessibilityCollectionItem prop on cell wrapper View
• Add accessibilityCollection (rowCount/columnCount) to ScrollView
• Add Flow types for AccessibilityCollection and AccessibilityCollectionItem
• Fix FlatList multi-column grid accessibility with proper row/column indices

Closes #30975

Summary:

This change improves accessibility for VirtualizedList and FlatList by enabling Android TalkBack to correctly announce item position (e.g., "item X of Y") and grid structure. It introduces support for accessibilityCollection and accessibilityCollectionItem, ensuring proper indexing for both single-column and multi-column lists.

Changelog:

[Android] [Added] - Enable TalkBack to announce item position in VirtualizedList and FlatList

Test Plan:

• Verified TalkBack announces "item X of Y" when navigating FlatList items on Android
• Tested both single-column and multi-column FlatList configurations
• Confirmed correct row/column indexing in grid layouts
• Ran existing test suite to ensure no regressions

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[javache]

It looks like a version of this landed a while back in #33180 but broke some internal signals and was never re-landed. Can you compare approaches?

[popsiclelmlm]

Leaving a few notes because this overlaps with the same area I investigated in #57016, and @javache asked about comparing approaches with #33180.

A few things look important before this approach can land:

1. The current Android scroll accessibility delegate reads more fields than this PR supplies. ReactScrollViewAccessibilityDelegate calls accessibilityCollection.getInt("itemCount") for the event, and the node-info path reads rowCount, columnCount, and hierarchical. It also expects visible collection items to carry an itemIndex for event.fromIndex / event.toIndex. This PR currently supplies rowCount/columnCount on the collection and rowIndex/columnIndex on items, but not itemCount, hierarchical, or itemIndex, so scroll accessibility events will not have the data the native code expects.

2. VirtualizedList builds a generated accessibilityCollection after spreading this.props, so it overwrites a user-provided accessibilityCollection. We should preserve explicit user props here, similar to how role / accessibilityRole should not be overwritten.

3. Multi-column FlatList still needs special handling. At the VirtualizedList layer, a multi-column FlatList is represented as rows, so the generated collection becomes rowCount=<row count>, columnCount=1. Passing accessibilityCollectionItem into renderItem info does not attach it to the rendered item root unless user code opts into that prop. That means grid items may still be announced as rows rather than individual row/column positions.

4. This changes the public JS API surface by adding accessibilityCollectionItem to ListRenderItemInfo / View accessibility props. If the goal is only internal list wiring, it may be better to keep this prop internal to the list implementation and avoid the extra API-review path.

#57016 takes a narrower pass at the same issue: it preserves user props, includes the fields expected by the current Android delegate, recursively finds tagged descendants for visible ranges, and keeps accessibilityCollectionItem as an internal wiring detail rather than adding it to the public renderItem contract.