Sensitive Notification Reveal Animation Preparations

This CL includes some setup for the Sensitive Notification Reveal Animation.

Test: Manual, i.e. checking sensitive reveal animation when face unlocking. With this change, the animation has still issues related to the notification size change when revealing the private content. Therefore the Flag is deactivated by default.
Bug: 243634602
Change-Id: Iddcc9b0555bfe77266847d687604c2611db099a6