Invert playNonAtomicComponent() as onlyPlayAtomicComponent()

This avoids the double negative we use in a few places, so should be clearer.
Also added some comments to explain what the animComponents are used for.

Change-Id: Ibd25bd12efce6553b377bbd9c0651e4f4ac3e498

src/com/android/launcher3/allapps/AllAppsTransitionController.java

@@ -162,7 +162,7 @@ public class AllAppsTransitionController implements StateHandler, OnDeviceProfil
             return;
         }
 
-        if (!config.playNonAtomicComponent()) {
+        if (config.onlyPlayAtomicComponent()) {
             // There is no atomic component for the all apps transition, so just return early.
             return;
         }