These new tests verify that all fields defined in UsageStats, UsageEvents.Event and IntervalStats are known fields. This is to ensure that when new fields are added to these objects or a refactoring is done, the fields are accounted for when persisting usage stats. Bug: 155935953 Test: atest UsageStatsPersistenceTest Test: atest IntervalStatsTest Change-Id: Ice65391d0af08b64db4ccaa046e57d9fca299319