Reduce usage of autorelease pools (#968)

* Reduce reliance on the autorelease pool

* changelog

* A few more places

* Use it in another place

Source/Layout/ASStackLayoutSpec.mm

@@ -160,7 +160,7 @@
     self.style.descender = stackChildren.back().style.descender;
   }
   
-  NSMutableArray *sublayouts = [NSMutableArray array];
+  auto sublayouts = [[NSMutableArray<ASLayout *> alloc] init];
   for (const auto &item : positionedLayout.items) {
     [sublayouts addObject:item.layout];
   }