Update deprecated Notification builder to new API

* Replace Notification.setLastEventInfo() and various variable
  assignments with the corresponding Notification.Builder API calls.
* Explicitly choose theme for getColor() using Context.getTheme() as
  previous getColor() method is deprecated as well.

Bug: 31218737
Test: TestTracker/63162/3975
Change-Id: I696cb7f07b50b04551e56c3b4a02fea87f23589c