Fix app switch regression

- SystemUI has STOP_APP_SWITCHES, which meant that
  checkAppSwitchAllowedLocked() would never block the launch of an
  activity after hitting the home button when launching from recents.
  However, Launcher does not have this permission, so quick launches of
  home/launcher-based-recents activity would be blocked (waiting for the
  app switch timeout). This is only apparent when we have the fallback
  3 button nav bar, since we do not stop app switches when swiping up.

  This CL enables the system defined recents activity to manage app
  switches.

Bug: 77152886
Test: Manual, enable three button nav bar, go home, double tap recents and
      then tap again to go home.
Test: atest FrameworksServicesTests:RecentTasksTest

Change-Id: I51959c2b0f8d8b7c5f184a1fdf15294b569f5a50