Udate sources for determining NSSL.headsUpAnimationsEnabled

Rely on the StatusBarState, and the isShadeFullyCollapsed signal to
match previous behavior before the refactor.

Bug: 325936094
Test: observe HUN intro/outro animations
Flag: ACONFIG com.android.systemui.notifications_heads_up_refactor
STAGING

Change-Id: Ie7a86a3d37a4c985ea7dbfe82e80210b3cd5a1ac