Pass CDC text as credential-only to BiometricPrompt

Invokes the new hidden API to allow the work authentication prompt to
supply specific text to BiometricPrompt for credential auth. This
allows the prompt to use work-specific language when verifying work
credentials, while retaining more generic language when authenticating
with biometrics.

Test: Work lock prompt shows "Enter your work ___" for credential
Test: Work lock prompt now shows "Verify it's you" for face

Bug: 149003660
Change-Id: Icab8e16702ca31d08fa8b0b00f0519c9a37f609f