Don't show notification private view too early

Don't show the notification private view  immediately
after authenticating with a biometric that can bypass
the lockscreen. We don't want to flash the private notification
right before we hide the notification shade because it looks
janky. Instead, wait to update it until after the keyguard
is done going away.

Test: atest SensitiveContentCoordinatorTest NotificationViewHierarchyManagerTest
Test: manually test with and w/o the new notification pipeline enabled
  1. add FP for security
  2. Settings > Notifications > Disable "Sensitive notifications"
  3. Post a notification that would be partially hidden as a sensitive
     notification
  4. Authenticate with FP on the LS (repeat 10x) times
  Expected: notifications don't flash their private views when entering
  the device
Bug: 212835832

Change-Id: I5ce4460043250aad4a5b0b0838e6f3b5ae6feb1d