Add flag to subscribe trust manager to primary auth events

This removes the need for user-facing primary auth fixtures such as
Keyguard/BiometricPrompt to manually report the primary auth events.
The event reports are cut off atomically with the subscription of
TrustManagerService to the primary auth events.

BUG: 323086607
Test: `atest TrustTests`
Test: `atest TrustManagerServiceTest`
Flag: android.security.should_trust_manager_listen_for_primary_auth
Change-Id: If578ac819d3f78b297c5de2cf7c6628ad8e0afb8