Change BiometricManager#hasEnrolledBiometrics to canAuthenticate

BiometricPrompt#authenticate and BiometricManager#canAuthenticate now
use the same logic to determine if the prompt can successfully be shown.

Before Android P, apps used FingerprintManager isHwAvail && hasEnrolled
before asking users to enable biometrics for their app. With
BiometricPrompt, which abstracts away individual biometric modalities,
developers need a way to determine if they should ask users to enable
biometrics for their app. Having separate checks is a nightmare due
to the untestable combinations of multi-biometric devices. This API change
makes it much more scalable since the logic will be done in the platform.

Fixes: 116823693

Test: manual test, returns status correctly

Change-Id: Ie0ecd139c9a39100b6dbc9bd85462400cb465f08