[ReactNative] Properly support overflow: 'visible' on ScrollView

Summary:
We need to unset `clipsToBounds` on both the wrapper and the inner custom
scroll view

@public

Test Plan:
`overflow: 'visible'` actually shows content outside the `ScrollView`
(e.g. for full-bleed horizontal scrollers/carousels).  It doesn't pick up
touches though, which is a wider issue.

React/Views/RCTScrollView.m

@@ -294,6 +294,12 @@ CGFloat const ZINDEX_STICKY_HEADER = 50;
   _scrollView.stickyHeaderIndices = headerIndices;
 }
 
+- (void)setClipsToBounds:(BOOL)clipsToBounds
+{
+  [super setClipsToBounds:clipsToBounds];
+  [_scrollView setClipsToBounds:clipsToBounds];
+}
+
 - (void)dealloc
 {
   _scrollView.delegate = nil;