Add a flag to enable unlocking private space using biometrics

The private space unlock flows currently only support
LSKF(PIN/Pattern/Password) to unlock the space. We want to add the
functionality to allow biometrics (face/fingerprint) to unlock private
space as well.

Test: m all_aconfig_declarations
Bug: 312184187
Change-Id: I71a83a20eae4e7f95f3362ea8692fea4ff2e9190