Create component used metrics in UsageStats

Created a new metrics called mLastTimeComponentUsed in UsageStats.
It is persisted and loaded as other metrics.

Bug: 175829712
Test: core/tests/coretests/src/android/app/usage/UsageStatsTest
Test: cts/UsageStatsTest
Test: UsageStatsDatabaseTest
Test: UsageStatsServiceTest
Test: UsageStatsPersistenceTest
Change-Id: I10cf5c40cf5955246a6a04e96ac0352b4ed29acd