Merge "Document the standby bucket guarantee" into sc-dev

         For more details, see <a

         href="{@docRoot}about/versions/12/behavior-changes-12#exact-alarm-permission">

         Exact alarm permission</a>.

         <p>Apps who hold this permission and target API level 31 or above, always stay in the

         {@link android.app.usage.UsageStatsManager#STANDBY_BUCKET_WORKING_SET WORKING_SET} or

         lower standby bucket.

         Applications targeting API level 30 or below do not need this permission to use

         exact alarm APIs.

     -->