Also apply freeze-task-list when starting an activity

- We previously only did this for startActivityFromRecents(), but for 3p
  launchers, we need to start the RecentsActivity mid-gesture and don't
  want to punt the excluded task from the front of the list

Bug: 137199105
Test: Install 3p Launcher, force-enable gesture nav, swipe up from
      exclude-from-recents activity

Change-Id: I7881ea103e83d28df1ec94d1874295188bed1064