This CL adds settings (and two toggle controls) that help configure
how trust (from Trust Agents) should be interpreted by the platform,
allowing them to function in a purely extend unlock mode (where they
can extend how long an already unlocked device stays unlocked, but
cannot unlock a locked device).
These are temporary settings to help with dogfooding the new behavior,
and will eventually be removed. b/120871688 below is the tracking bug
to remove them.
Bug: 111435975
Bug: 120871688
Test: Tested with SmartLock modalities to confirm behavior in both
legacy and extend unlock modes is WAI.
Change-Id: If25098520ba98e82c98cc51fb226d8f2ce1aba80
b6dad935ec