Prepare BiometricService for migration to a module

Created an interface, IBiometricAuthenticator, that encapsulates
fingerprint, iris, and face services. Removed direct references to these
services from BiometricService.

The interface will allow new biometric authenticators to be integrated
with BiometricService without modifying its code.

Bug: 141025588
Test: Face Unlock works E2E
Test: Works with BiometricPromptDemo
Test: atest BiometricServiceTest
Change-Id: I564ccdccbfe25b2c41f92f7e91eedde6acdeeed4