Substantially improve behavior of nested Table & Collection Nodes

This ensures memory cleanup happens correctly and introduces a new test project
to support developing new features while stressing tough use cases for correctness.

examples/VerticalWithinHorizontalScrolling/Sample/GradientTableNode.mm

@@ -0,0 +1,76 @@
+/* This file provided by Facebook is for non-commercial testing and evaluation
+ * purposes only.  Facebook reserves all rights not expressly granted.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * FACEBOOK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
+ * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+ * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#import "GradientTableNode.h"
+#import "RandomCoreGraphicsNode.h"
+#import "AppDelegate.h"
+
+#import <AsyncDisplayKit/ASDisplayNode+Subclasses.h>
+
+#import <AsyncDisplayKit/ASStackLayoutSpec.h>
+#import <AsyncDisplayKit/ASInsetLayoutSpec.h>
+
+@interface GradientTableNode ()
+{
+  ASTableNode *_tableNode;
+  CGSize _elementSize;
+}
+
+@end
+
+
+@implementation GradientTableNode
+
+- (instancetype)initWithElementSize:(CGSize)size
+{
+  if (!(self = [super init]))
+    return nil;
+
+  _elementSize = size;
+
+  _tableNode = [[ASTableNode alloc] initWithStyle:UITableViewStylePlain];
+  [self addSubnode:_tableNode];
+  
+  return self;
+}
+
+- (void)didLoad
+{
+  [super didLoad];
+  _tableNode.view.asyncDelegate = self;
+  _tableNode.view.asyncDataSource = self;
+  
+  ASRangeTuningParameters rangeTuningParameters;
+  rangeTuningParameters.leadingBufferScreenfuls = 1.0;
+  rangeTuningParameters.trailingBufferScreenfuls = 0.5;
+  [_tableNode.view setTuningParameters:rangeTuningParameters forRangeType:ASLayoutRangeTypeRender];
+}
+
+- (NSInteger)tableView:(UITableView *)tableView numberOfRowsInSection:(NSInteger)section
+{
+  return 100;
+}
+
+- (ASCellNode *)tableView:(ASTableView *)tableView nodeForRowAtIndexPath:(NSIndexPath *)indexPath
+{
+  RandomCoreGraphicsNode *elementNode = [[RandomCoreGraphicsNode alloc] init];
+  elementNode.preferredFrameSize = _elementSize;
+  return elementNode;
+}
+
+- (void)layout
+{
+  [super layout];
+  
+  _tableNode.frame = self.bounds;
+}
+
+@end