Fix NotificationLaunchAnimator in the refactor.

We hand the RemoteAnimationTarget to the launch animator, so we need to set it to alpha = 0f to ensure it does not flicker in the meantime.

Since the WmLockscreenVisibilityManager retains control over the remote animation lifecycle, we also need to make sure to keep the animation alive until it's done running, or it'll jump-cut in.

Bug: 278086361
Test: atest KeyguardSurfaceBehindInteractorTest
Flag: ACONFIG com.android.systemui.keyguard_wm_state_refactor DEVELOPMENT
Change-Id: I84714e31ca13c22409e294135b8cd48997bf749e