Don't wait until next fetch of recent tasks to reset the task list

- Launcher keeps track of a change id tracking the task stack changed
  callback, and uses this change id to determine whether to fetch a new
  task list.  This change ensures that we always reset the task list
  after the timeout, and notifies SysUI of the task stack change when
  the task list is unfrozen.

Bug: 130290840
Test: Quickswitch to next task, try to quickswitch again but settle on the
      same task, then wait and ensure that the tasks have been reset

Change-Id: Ib4ac7df16f891c31fa73b74014ce8084a43dafe5