* 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.
Introduces ASLayoutRangeModeVisibleOnly, allowing the preservation of decoded backing stores without any extra padding to
strictly minimize memory usage while supporting immediate re-display of content. Set visible range controllers to this mode
upon app suspend / memory warning, while more aggressively clearing others to the ASLayoutRangeModeLowMemory mode.
By default, when the app is running and recieves a memory warning, we set the range mode for non-visible controllers to
ASLayoutRangeModeVisibleOnly. This is because, unlike in the app suspend case where on app resume we can restore controllers
from LowMemory to VisibleOnly, the memory warning doesn't provide a good opportunity to do this.
A new +Beta API to control this behavior is called +setRangeModeForMemoryWarnings:, as some apps may prefer to use LowMemory
in the memory warning scenario. For these apps, optimal user experience will require manually setting the range mode back
to some larger value as the user navigates the app, or they will encounter controllers that are temporarily blank and need
a moment to re-display their contents as they start to become visible.
