Fix crash in RCTTextView related to NSLayoutManager

Summary: In a prior diff we removed some code that fixed an occasional crash in RCTTextView. This diff brings back the code, adapted from microsoft#523.

Test Plan:
Open the Text section of RNTester several times and verify no crash:
|Before|After|
|{F612971452}|{F612971479}|

Reviewers: skyle

Reviewed By: skyle

Subscribers: eliwhite

Differential Revision: https://phabricator.intern.facebook.com/D28166631

Tasks: T78743077

Signature: 28166631:1620086528:d359ab6e0c3477f2e52784534b6763156b33b1e5

Author: lyahdav

Libraries/Text/Text/RCTTextView.m

@@ -231,6 +231,17 @@ - (void)setTextStorage:(NSTextStorage *)textStorage
 
   [_textView replaceTextContainer:textContainer];
 
+  // On macOS AppKit can throw an uncaught exception
+  // (-[NSConcretePointerArray pointerAtIndex:]: attempt to access pointer at index ...)
+  // during the dealloc of NSLayoutManager.  The textStorage and its
+  // associated NSLayoutManager dealloc later in an autorelease pool.
+  // Manually removing the layout managers from textStorage prior to release
+  // works around this issue in AppKit.
+  NSArray<NSLayoutManager *> *managers = [[textStorage layoutManagers] copy];
+  for (NSLayoutManager *manager in managers) {
+    [textStorage removeLayoutManager:manager];
+  }
+
   _textView.minSize = contentFrame.size;
   _textView.maxSize = contentFrame.size;
   _textView.frame = contentFrame;