3/Removing unnecessary filtering logic for recent tasks in SystemUI

- Remove all code related to last-stack-active-time, quiet profile task
  handling, and visible task range filtering
- Remove the notion of firstActiveTime since that was only used to filter
  tasks in SystemUI, also convert lastActiveTime to elapsed real time since
  it is only used in the system to order active tasks, and in SystemUI as
  a part of the TaskKey for caching purposes (it is no longer used to
  determine the last visible task based on time)

Bug: 34270611
Test: runtest --path frameworks/base/services/tests/servicestests/src/com/android/server/am/RecentTasksTest.java
Change-Id: I44d494a521f60f302e0976fcf33490fe837f7cdb