Add UsageStatsQueryHelper to People Service

It processes these UsageStats events:
- SHORTCUT_INVOCATION
- NOTIFICATION_INTERRUPTION
- LOCUS_ID_SET
- ACTIVITY_PAUSED/STOPPED/DESTROYED

The in-app conversation is counted from the LOCUS_ID_SET event to the
next LOCUS_ID_SET event, or the associated Activity is
paused/stopped/destroyed.

Change-Id: I5ecb78e61f9f69129e7fa9cc67e9e94b2148fcda
Test: Manual tests \
    atest com.android.server.people.data.UsageStatsQueryHelperTest \
    atest com.android.server.people.data.DataManagerTest \
    atest com.android.server.people.data.CallLogQueryHelperTest \
    atest com.android.server.people.data.ConversationInfoTest \
    atest com.android.server.people.data.ConversationStoreTest
Bug: 146522621