Add 'automaticallyAdjustsScrollIndicatorInsets' prop to ScrollView (for iOS)

Summary:
In iOS 13 Apple added a new property to UIScrollView that "automatically" alters the scroll indicator insets in a fashion similar to the way 'contentInsetAdjustmentBehavior' alters content insets.  See here for iOS documentation:
https://developer.apple.com/documentation/uikit/uiscrollview/3198043-automaticallyadjustsscrollindica?language=objc

The OS default value for this property is `true`, which we preserve. When set to `false`, the behavior matches iOS <= 12.

Closes #28140

Author: justinwh

Libraries/Components/ScrollView/ScrollView.js

@@ -171,6 +171,12 @@ type IOSProps = $ReadOnly<{|
    * @platform ios
    */
   automaticallyAdjustContentInsets?: ?boolean,
+  /**
+   * Controls whether iOS should automatically adjust the scroll indicator
+   * insets. The default value is true. Available on iOS 13 and later.
+   * @platform ios
+   */
+  automaticallyAdjustsScrollIndicatorInsets?: ?boolean,
   /**
    * The amount by which the scroll view content is inset from the edges
    * of the scroll view. Defaults to `{top: 0, left: 0, bottom: 0, right: 0}`.

Libraries/Components/ScrollView/ScrollViewNativeComponent.js

@@ -26,6 +26,7 @@ const ScrollViewNativeComponent: HostComponent<Props> = NativeComponentRegistry.
       alwaysBounceHorizontal: true,
       alwaysBounceVertical: true,
       automaticallyAdjustContentInsets: true,
+      automaticallyAdjustsScrollIndicatorInsets: true,
       bounces: true,
       bouncesZoom: true,
       canCancelContentTouches: true,

Libraries/Components/ScrollView/ScrollViewNativeComponentType.js

@@ -21,6 +21,7 @@ export type ScrollViewNativeProps = $ReadOnly<{
   alwaysBounceHorizontal?: ?boolean,
   alwaysBounceVertical?: ?boolean,
   automaticallyAdjustContentInsets?: ?boolean,
+  automaticallyAdjustsScrollIndicatorInsets?: ?boolean,
   bounces?: ?boolean,
   bouncesZoom?: ?boolean,
   canCancelContentTouches?: ?boolean,

Libraries/Components/ScrollView/ScrollViewViewConfig.js

@@ -24,6 +24,7 @@ const ScrollViewViewConfig = {
     alwaysBounceHorizontal: true,
     alwaysBounceVertical: true,
     automaticallyAdjustContentInsets: true,
+    automaticallyAdjustsScrollIndicatorInsets: true,
     bounces: true,
     bouncesZoom: true,
     canCancelContentTouches: true,

React/Views/ScrollView/RCTScrollView.m

@@ -928,6 +928,18 @@ -(type)getter                                           \
 RCT_SET_AND_PRESERVE_OFFSET(setZoomScale, zoomScale, CGFloat);
 RCT_SET_AND_PRESERVE_OFFSET(setScrollIndicatorInsets, scrollIndicatorInsets, UIEdgeInsets);
 
+#if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 130000 /* __IPHONE_13_0 */
+- (void)setAutomaticallyAdjustsScrollIndicatorInsets:(BOOL)automaticallyAdjusts API_AVAILABLE(ios(13.0))
+{
+  // `automaticallyAdjustsScrollIndicatorInsets` is available since iOS 13.
+  if ([_scrollView respondsToSelector:@selector(setAutomaticallyAdjustsScrollIndicatorInsets:)]) {
+    if (@available(iOS 13.0, *)) {
+      _scrollView.automaticallyAdjustsScrollIndicatorInsets = automaticallyAdjusts;
+    }
+  }
+}
+#endif
+
 #if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 110000 /* __IPHONE_11_0 */
 - (void)setContentInsetAdjustmentBehavior:(UIScrollViewContentInsetAdjustmentBehavior)behavior API_AVAILABLE(ios(11.0))
 {

React/Views/ScrollView/RCTScrollViewManager.m

@@ -102,6 +102,9 @@ - (UIView *)view
 RCT_EXPORT_VIEW_PROPERTY(onMomentumScrollBegin, RCTDirectEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(onMomentumScrollEnd, RCTDirectEventBlock)
 RCT_EXPORT_VIEW_PROPERTY(inverted, BOOL)
+#if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 130000 /* __IPHONE_13_0 */
+RCT_EXPORT_VIEW_PROPERTY(automaticallyAdjustsScrollIndicatorInsets, BOOL)
+#endif
 #if defined(__IPHONE_OS_VERSION_MAX_ALLOWED) && __IPHONE_OS_VERSION_MAX_ALLOWED >= 110000 /* __IPHONE_11_0 */
 RCT_EXPORT_VIEW_PROPERTY(contentInsetAdjustmentBehavior, UIScrollViewContentInsetAdjustmentBehavior)
 #endif