Teach DeskClock about file-based encryption. - DO NOT MERGE

Bug: 25860525

When running on a device that supports FBE, all persisted data is
stored in the device-encrypted area.  Also mark core components as
being encryption-aware so we can schedule and trigger alarms while
the user is still locked.

Change-Id: I7517be716468b09eed0c007600abd1937e203449
(cherry picked from commit 4a025d30)