Start UDFPS sensors only after BiometricPrompt UI is showing

Since UDFPS sensors have a UI affordance, and the affordance is
controlled by FingerprintAuthenticationClient, start the prepared
sensor only after the BiometricPrompt dialog is done animating.

Plumbing-wise, adds:
1) Adds AuthSession.STATE_AUTH_STARTED_UI_SHOWING
2) Adds IBiometricSysuiReceiver#onDialogAnimatedIn

Since not all sensors are started immediately anymore, adds
logic in BiometricScheduler when attempting to cancel auth
for a sensor that's waiting for cookie (HAL still idle).

Fixes: 171931476
Test: atest com.android.server.biometrics
Test: atest com.android.systemui.biometrics

Change-Id: Iaedc26c51e274614ac2af6ebd98afe26263dad81