Implemented and integrated AuthService

AuthService in its current form is a thin wrapper around
BiometricService. It initializes BiometricService in onStart();
registers fingerprint, face, and iris authenticators; and forwards all
of the incoming calls to the corresponding methonds in BiometricService.

The next step will be to move non-biometric related functionality from
BiometricService to AuthService, and turn BiometricService into a module
with a stable API.

Bug: 141025588
Test: atest AuthServiceTest
Test: atest BiometricServiceTest
Test: BiometricPrompt works in BiometricPromptDemo
Change-Id: Ia861b7c2d80bfca386c3e0b44ec35b4aca3b0ffc