Add feature flag for biometric property verification

The feature flag enable_biometric_property_verification under the
biometrics namespace is checked before collecting/verifying biometric
sensor properties.

If the flag is false (the default), no data will be logged; otherwise if
the flag is true.

Bug: 259566704
Bug: 204801320
Test: atest BinaryTransparencyServiceTest
Test: Mannually set the flag to true/false via:
      adb shell device_config put biometrics
          enable_biometric_property_verification true/false
      Then check whether data is logged via:
      m statsd_testdrive && statsd_testdrive 587
Change-Id: Ic0e6fe00409c11a4f30748598b73de1a7c7d7422