package:objective_c v9.6.2

• Fix potential memory leaks when converting a Dart String to a NSString
  (via toNSString or the NSString constructor) because the created
  NSString was added to the autorelease pool.
• Fix potential memory leaks when calling the following Objective-C collection
  factories because the created collection was added to the autorelease pool:
  • NSArray.filled
  • NSArray.of
  • NSMutableArray.filled
  • NSMutableArray.of
  • NSDictionary.of
  • NSDictionary.fromEntries
  • NSMutableDictionary.of
  • NSMutableDictionary.fromEntries
  • NSSet.of
  • NSMutableSet.of
• Fix potential memory leaks when converting a Dart int, double, num or
  bool to a NSNumber (via toNSNumber) because the created NSNumber was
  added to the autorelease pool.
• Replace NSDate.dateWithTimeIntervalSince1970 with
  NSDate.alloc().initWithTimeIntervalSince1970. NSDate uses pointer
  tagging rather than reference counting for the entire range of DateTime
  so this change is for consistency (and not rely on an implementation
  detail), not correctness.
• Fix a crash in the NSInputStream returned by toNSInputStream: reading
  from or closing the stream after its Dart side had already closed it raised
  NSInternalInconsistencyException ("DartInputStreamAdapter:
  Dart_PostCObject_DL failed") and aborted the process. NSURLSession does
  exactly that with a request body stream when the request completes with an
  error or is cancelled right after it starts. close is now idempotent, and
  a read on a closed stream (or one whose Dart owner is gone) fails with -1
  instead of asserting.
• Fix a bug where toNSData/toNSMutableData added the returned NSData
  to the autorelease pool.
• Fix a bug where toNSInputStream would create cycles between Dart and
  Objective-C.