Update exact alarm reason code in atom tests

The test now uses USE_EXACT_ALARM, which has a different reason code to
differentiate from SCHEDULE_EXACT_ALARM.
Split the alarm atom tests to a separate device side APK for easier
maintenance.

Test: atest CtsStatsdAtomHostTestCases:AlarmStatsTest

Bug: 231661615
Change-Id: I9309ef437e415fcbca3b2ab9350a79fa24135001
10 files changed