2/n: Keep track of IBiometricsFace@1.0 challenge interruptions

IBiometricsFace@1.0 only supports a single in-flight challenge.
Currently, challenge owners paths are designed to never conflict
lifecycle-wise. However, to decouple resetLockout (which relies
on challenge) from the critical user unlock path, we need to
keep track of challenge interruptions, and notify clients when
an interruption starts/finishes.

This change only adds the infrastructure for tracking challenge
interruptions. A following change will make use of this.

Bug: 145978626
Test: Builds
Change-Id: I708312cafad29614e3708b5c606ae8a90704ac66