expo: use expo-hinge and ArrangementView for foldables when moving to SDK 58 #709

Expo SDK 58 (on npm as next, 58.0.6) ships first-party foldable support:

• expo-hinge (expo/expo#50912, Android in #51201): getHinge(), addHingeListener(), isAvailable() and useHinge(). A hinge has an angle in degrees and a status of closed, partiallyOpen, fullyOpen or unknown, and is null on a device without one.
• ArrangementView in @expo/ui (SwiftUI): a container that places a primary and a secondary view around the fold, for layout.
• onHingeChange modifier for @expo/ui views, with worklet callbacks (#50909, #50910).

Foldable in @ng-native/expo/foldable wraps the community expo-foldables today, and npm's expo-hinge is still a placeholder ("Reserved name. Use expo-foldables."), so nothing can change on SDK 57.

When the workspace moves to SDK 58:

1. Have Foldable read expo-hinge, keeping expo-foldables as a fallback so an app that has it keeps working. The posture maps directly (partially-open and partiallyOpen, and so on).
2. Add <arrangement-view> alongside the other @expo/ui components, since Apple's guidance is that layout around the fold goes through the arrangement and reserved-region APIs, and the hinge is for interactions and effects.
3. Add an (hingeChange) binding for @expo/ui views, matching onHingeChange.
4. Update examples/foldbook and the foldable docs page.

Happy to take this on once SDK 58 is latest.