Add plumbing and placeholder screens for parental consent flow.

Bug: 188847063
Test: adb shell am start -a android.settings.BIOMETRIC_ENROLL --ez require_consent true
Test: atest com.android.settings.biometrics.ParentalConsentHelperTest
Change-Id: Ie136036d5f550775fd0b021979581a5d222f1b68
10 files changed