Update launch cookie when moving a task to front

- We're using the launch cookies to track app launches, and in the
  case that a task is brought forward the starting activity is not
  used (currently the launch cookie is only set there).  In this
  case we should update the top activity of the task with the new
  launch cookie.

Bug: 129067201
Test: atest ActivityStarterTests
Change-Id: I563e8aa107d6423672b7dfc2313fa0f3dc33a517