Fix HUN not showing after unlocking with unlock button

We have a race condition between LockscreenToGoneTransitionViewModel.notificationAlpha and isTransitioningToHiddenKeyguard, which leads to NSSL being left
transparent when unlocking too fast (approximately 200ms, longer
than unlocking by long-pressing the unlock button).

This is the first phase of fix: decreasing the duration of
LockscreenToGoneTransitionViewModel from 200ms to 100ms, making
it shorter than unlocking by long-pressing the unlock button.
The next phase should find a way to prevent this race condition.

Change-Id: I05cff92a3715e3be75b19b5741b301a112a54490
Test: LockscreenToGoneTransitionViewModelTest
Flag: EXEMPT bugfix
Fix: 357316448