Assume convenience for biometrics not configured in R

This change restores R biometric behavior for devices that:
- Declare FEATURE_FINGERPRINT or FEATURE_FACE
- Have an empty config_biometric_sensors in config.xml
- Report ro.board.[first_]api_level as 30 (R)

The behavior is restored by assuming that the device has biometrics
sensors of the convenience strength class.

Bug: 200005662
Bug: 198692048
Test: blueline + R vendor w/o the config + S GSI
Change-Id: I2ae8b746bb5247b5bb6ef9929b3a11ad5403ca48
Merged-In: I2ae8b746bb5247b5bb6ef9929b3a11ad5403ca48