provide public hook to programatically turn on voiceover

Summary:
Changelog: [Internal]

https://fb.workplace.com/groups/rn.support/posts/6677051292343429

ax team is building a tool to extract information about the views for design reviewers, and RN has some AX information that is not working atm because of dependency on whether voiceover is on or not. so, this will give them the ability to programmatically set that field and hopefully be able to get accurate ax info

Reviewed By: ikenwoo

Differential Revision: D31010566

fbshipit-source-id: 4c8a33fce40266b270dd5994442c8472ca88f5dd

React/CoreModules/RCTAccessibilityManager+Internal.h

@@ -0,0 +1,21 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#import "RCTAccessibilityManager.h"
+
+#import <React/RCTDefines.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+RCT_EXTERN_C_BEGIN
+
+// Only to be used for testing and internal tooling. Do not use this in production.
+void RCTAccessibilityManagerSetIsVoiceOverEnabled(RCTAccessibilityManager *accessibiltyManager, BOOL isVoiceOverEnabled);
+
+RCT_EXTERN_C_END
+
+NS_ASSUME_NONNULL_END

React/CoreModules/RCTAccessibilityManager.mm

@@ -6,6 +6,7 @@
  */
 
 #import "RCTAccessibilityManager.h"
+#import "RCTAccessibilityManager+Internal.h"
 
 #import <FBReactNativeSpec/FBReactNativeSpec.h>
 #import <React/RCTBridge.h>
@@ -183,9 +184,14 @@ RCT_EXPORT_MODULE()
 
 - (void)voiceVoiceOverStatusDidChange:(__unused NSNotification *)notification
 {
-  BOOL newIsVoiceOverEnabled = UIAccessibilityIsVoiceOverRunning();
-  if (_isVoiceOverEnabled != newIsVoiceOverEnabled) {
-    _isVoiceOverEnabled = newIsVoiceOverEnabled;
+  BOOL isVoiceOverEnabled = UIAccessibilityIsVoiceOverRunning();
+  [self _setIsVoiceOverEnabled:isVoiceOverEnabled];
+}
+
+- (void)_setIsVoiceOverEnabled:(BOOL)isVoiceOverEnabled
+{
+  if (_isVoiceOverEnabled != isVoiceOverEnabled) {
+    _isVoiceOverEnabled = isVoiceOverEnabled;
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wdeprecated-declarations"
     [[_moduleRegistry moduleForName:"EventDispatcher"] sendDeviceEventWithName:@"screenReaderChanged"
@@ -350,6 +356,15 @@ RCT_EXPORT_METHOD(getCurrentVoiceOverState
   return std::make_shared<facebook::react::NativeAccessibilityManagerSpecJSI>(params);
 }
 
+#pragma mark - Internal
+
+void RCTAccessibilityManagerSetIsVoiceOverEnabled(
+    RCTAccessibilityManager *accessibilityManager,
+    BOOL isVoiceOverEnabled)
+{
+  [accessibilityManager _setIsVoiceOverEnabled:isVoiceOverEnabled];
+}
+
 @end
 
 @implementation RCTBridge (RCTAccessibilityManager)