Adjust recents onboarding logic

- After dismissing, don't show again until 5 app launches
- Don't count the same task id towards that 5 (or the 2 before
  showing the first time)

Test: manual, launch a couple apps and verify onboarding shows;
continues showing until I dismiss it; shows again after launching
5 apps (different activities in the same app don't count)

Bug: 73392035
Bug: 70180942
Change-Id: Icff567e3418097c3503d2f322cf829a9efc195e7