AccessibilityInfo API Improvements

[6TELOIV]

The AccessibilityInfo api exposes enough information for most apps to do OK with regards to accessible design; however, the core system has two main issues

Clunky Interface

The boolean getter functions of isXYZ (and the differently named prefersCrossFadeTransitions) only provide async access to the value for a single render. If developers want their app to remain in sync with the system settings, they must use the event listener to maintain that state themselves.

Instead, the API should expose this info through hooks, such as useBoldTextEnabled(), or usePreferesCrossFadeTransitions(), simplifying consumer code. I previously documented this idea in #869.

Missing flags

The API currently is missing the following accessibility flags from iOS:

• accessibilityAssistiveAccessEnabled
• accessibilityDimFlashingLights
• accessibilityDifferentiateWithoutColor
• accessibilityLargeContentViewerEnabled
• accessibilityPlayAnimatedImages
• accessibilityQuickActionsEnabled
• accessibilityShowButtonShapes
• accessibilitySwitchControlEnabled

And for Android, it is missing:

• isAudioDescriptionRequested
• isHighContrastTextEnabled

Implementation details

On iOS, each of those has their own "DidChangeNotification" types that can be used the same way react native currently handles.

On Android, an AccessibilityServicesStateChangeListener can be used to drive hooks and sync system state.