Ensure profile-specific PiP notification is shown.

- Pipe through user id when an activity is pinned, to ensure we show the
  right notification with the correct profile badge that launches into the
  correct profile's PiP settings.

Bug: 65417722
Test: Enter PiP for work profile app, ensure that it shows the notification
      for that profile, and launches the profile-specific PiP settings.

Change-Id: I62b8e1b23cb81bfc60c93f452cf950ab06cbf32d