Base "seen" logic on shade expansion and heads up

Before: all notifications are marked as seen when device is unlocked for 5 seconds

After: HUNs are immediately marked as seen, opening the shade will immediately mark all notifications as seen.

Fixes: 267963644
Test: CtsVerifier > Notification Privacy Test
Test: atest KeyguardCoordinatorTest
Change-Id: I71ef1b7a56c125ac8a5182f9a86282f95b8f9d08