* Improve Accessibility Implementation
- Fixes calculations for accessibilityFrame of ASAccessibilityCustomAction and ASAccessibilityElement
- Fix crash for accessibility elements within layer backed nodes
- Fix accessibility action label updating after other actions change the accessibility label of the corresponding node
* Address comments
* Refactored `accessibleElements` to `accessibilityElements`, and removed the re-definition of the property.
With this refactor, the field can now be used as a single access point into the accessibility elements of a view. Also, removing the re-definition of the property in _ASDisplayViewAccessibility.h enables us to make use of the field and its associated helper methods directly from the `UIAccessibilityContainer` API rather than rolling our own implementation.
* Added tests for the accessors to ASDisplayView.accessibilityElements.
* Commented out tests for older a11y accessors & added relevant warnings.
Also added assertions that the getter and setter for the accessibilityElements
property are used only on the main thread.
Michael Schneider
Eric Scheers
Max Wang
Kevin
Jia Wern Lim