2611 rename fetch data (#2689)

* Replace fetch data with preload terminology
- Deprecate `-fetchData` and `-clearFetchedData` in favor of `-preload` and `-clearPreloadedData`
- Move `-setNeedsPreload`, `-recursivelyPreload` and `-recursivelyClearPreloadedData` to ASDisplayNode+FrameworkPrivate.h
- Update internal implementation, comments and tests

* Folllow up on #2642:
- Remove -preload and -clearPreloadedData in favor of -didEnterPreloadState and -didExitPreloadState.
- -didEnterPreloadState and -didExitPreloadState call the deprecated -fetchData and -clearFetchedData methods if they are overriden.

* Missed one in a test

* Get rid of behavior change for now.

* Revert more behavior changes, fix tests.

* Don't need these anymore.

AsyncDisplayKit/ASDisplayNode+Subclasses.h

@@ -323,23 +323,6 @@ NS_ASSUME_NONNULL_BEGIN
  */
 @property (nonatomic, readonly, assign, getter=isInHierarchy) BOOL inHierarchy;
 
-/**
- * @abstract Indicates that the node should fetch any external data, such as images.
- *
- * @discussion Subclasses may override this method to be notified when they should begin to fetch data. Fetching
- * should be done asynchronously. The node is also responsible for managing the memory of any data.
- * The data may be remote and accessed via the network, but could also be a local database query.
- */
-- (void)fetchData ASDISPLAYNODE_REQUIRES_SUPER;
-
-/**
- * Provides an opportunity to clear any fetched data (e.g. remote / network or database-queried) on the current node.
- *
- * @discussion This will not clear data recursively for all subnodes. Either call -recursivelyClearFetchedData or
- * selectively clear fetched data.
- */
-- (void)clearFetchedData ASDISPLAYNODE_REQUIRES_SUPER;
-
 /**
  * Provides an opportunity to clear backing store and other memory-intensive intermediates, such as text layout managers
  * on the current node.