[Biometric Onboarding & Edu] Update Set up Face Unlock page

Update icons, strings and layouts for new UX design

Bug: 370940762
Test: manual:
      Pre condition - no face enrolled
      Go Settings>Security & privacy>Device unlock>Face unlock
Test: atest FaceEnrollTest
Flag: com.android.settings.flags.biometrics_onboarding_education
Change-Id: Ie469c47005afb941f5646a2f790736362c23c697