Clean up biometric system server

1) BiometricService / AuthService always need to be started, since on
   Android 11 and later, the public credential auth API comes through this
   path.

2) Consolidate getAuthenticatorId() and expose via AuthService. This is
   used only by the platform during key generation. Instead of asking
   each individual service, AuthService will return a list of IDs for
   sensors which are enrolled and meet the required strength.

Test: atest com.android.server.biometrics
Test: fingerprint device, CtsVerifier biometric section
Test: face unlock device, CtsVerifier biometric section
Test: remove biometrics from device, CtsVerifier biometric section

Bug: 148419762
Bug: 149795050

Change-Id: I2c5385b1cd4f343fabb0010e1fe6fb1ea8283391