Support metrics logging for face onboarding

Collect OnboardingEvent data from each face onboarding setting page and
send data to statsd and setupwizard.

Bug: 370940210
Test: atest FaceStatusUtilsTest FaceSafetySourceTest
Flag: com.android.settings.flags.biometrics_onboarding_education

Change-Id: I9af9c6d22782f46fd77820d30faaf54f95e85e37