Simplify aodVisibility to reflect whether we're in KeyguardState.AOD.

isDozing/isAodAvailable/wakeAndUnlocking are all taken into account now whenever we decide to transition to/from AOD.

Fixes: 330475572
Test: screen off/on with and without flexi enabled, while locked and unlocked
Flag: com.android.systemui.keyguard_wm_state_refactor
Change-Id: Ia7686d1093a33f73afad4e05c729a921e77288c0