<UserEventLogging> Log app launches

b/26494415

1) Current Logger can capture taps from
- homescreen
- folder inside homescreen
- apps prediction
- all apps a-z
- tap from hotseat
2) Deprecate LauncherCallback methods that is no longer needed

Future CL.
3) Stats and Logger will be merged. Bundle used for Stats can be
replaced with LauncherLogProto
4) Logging anything else other than app launches

Change-Id: Id52eb615f66142017b5c490a220ce6654d325681

src/com/android/launcher3/config/FeatureFlags.java

@@ -35,4 +35,5 @@ public final class FeatureFlags {
     public static boolean LAUNCHER3_LEGACY_WORKSPACE_DND = false;
     public static boolean LAUNCHER3_ICON_NORMALIZATION = true;
     public static boolean LAUNCHER3_CLIPPED_FOLDER_ICON = false;
+    public static boolean LAUNCHER3_LEGACY_LOGGING = false;
 }