Send widget added and removed events to AiAi.

-Pass the widgets on workspace as an extra List<AppTargetEvents> while
 creating prediction session.
-Notify the session about widget added/removed events after creation.

Bug: 186648032
Test: Manually checked events are received
Change-Id: I4de6c011a1e24c129a3e995ddba16bfc55074939
4 files changed