Define Secure Lock Device API surface

Secure Lock is a new feature that enables users to remotely lock
down their mobile device via authorized clients into an enhanced
security state, which restricts access to sensitive data (app
notifications, widgets, quick settings, assistant, etc) and requires
both credential and biometric authentication for device entry.

This change introduces a new AuthenticationPolicyManager, which
external clients will use to call into SecureLockDeviceService via
AuthenticationPolicyService. SecureLockDeviceService implements the new
enableSecureLockDevice and disableSecureLockDevice API methods, which
currently have a placeholder no-op implementation that will be filled
out at a later time.

Bug: 373422357
API-Coverage-Bug: 376456619
Flag: android.security.secure_lockdown
Test: atest AuthenticationPolicyServiceTest
Ignore-AOSP-First: adding flag to security package
Change-Id: I7d2c97a8f51cb8a4475761a6c04ce9f32b38fd19