[flexiglass] Register KeyguardService callbacks with more classes

If Flexiglass is enabled, still register it with KeyguardStateCallbackInteractor or with KeyguardViewMediator in addition to KeyguardStateCallbackStartable.

Initially, I thought this would fix b/419895698 but it didn't appear to.
Either way, this is a positive thing to do.

Bug: 419895698
Flag: com.android.systemui.scene_container
Test: not tested
Change-Id: I7c1726c4411abf14dbd7dcd05ad182428e6ea2d3