Implement sharesheet ranking in PeopleService. Ranking is only based on

recency of past sharing for the moment.

Bug: 149822311
Test: atest com.android.server.people.data.DataManagerTest
Test: atest com.android.server.people.data.ShareTargetPredictorTest
Change-Id: I90d1b3f488b34fede7d577dc04832b976f4a1bbb