Add logging for notifications.

- Log notification launches
- Log notification swipes
- Fix logDragNDrop() to only log if the pre-drag ends (so it doesn't
  log a long-press that only shows shortcuts without dragging).
- Add shortcut rank to logs when launching deep shortcuts, where 0
  is the shortcut closest to the app icon (highest rank).

Bug: 34770729
Bug: 32410600
Change-Id: I99dcef9b6a71da2ef58e32397702bb137407b10f
diff --git a/protos/launcher_log.proto b/protos/launcher_log.proto
index 33041db..c42b142 100644
--- a/protos/launcher_log.proto
+++ b/protos/launcher_log.proto
@@ -64,6 +64,7 @@
   DEEPSHORTCUT = 5;
   SEARCHBOX = 6;
   EDITTEXT = 7;
+  NOTIFICATION = 8;
 }
 
 // Used to define what type of container a Target would represent.