fix(PointAnnotation): fix nested children not rendering on New Architecture (Fabric)

[mfazekas]

Fixes #3682

In React Native's New Architecture (Fabric), a View inside PointAnnotation can get its children lifted up to become direct siblings in the native child list. This triggers the "supports max 1 subview other than a callout" error and causes the bitmap snapshot to only capture the empty outer View — nested content (e.g. Text labels) disappears.

Root cause: Fabric's view flattening optimization removes collapsable Views from the native hierarchy and reparents their children to the nearest non-flattened ancestor — in this case, PointAnnotation itself.

Fix: Wrap content children in a View collapsable={false} inside PointAnnotation.tsx. The native layer always sees exactly one content child regardless of how deeply the user nests views. Callout children are kept as direct native siblings (the native side identifies them by type).

Also removes the manual collapsable={false} workaround that was added to the PointAnnotationAnchors example — the library now handles this internally.

Reproducer (before fix)

<Mapbox.PointAnnotation id="test" coordinate={[0, 0]}>
  <View style={{ backgroundColor: 'blue', width: 50, height: 50 }}>
    <Text>label</Text>
  </View>
</Mapbox.PointAnnotation>

On RN 0.76+ with New Architecture: only the blue box renders, Text is missing, and the console logs PointAnnotation supports max 1 subview other than a callout.