Track notification clicked events in UsageStats

Expose some of the new events as SystemApi.

Make some of the timeouts configurable in AppStandbyController.

Make NOTIFICATION_SEEN event upgrade app to WORKING_SET for
12 hours. This is not perfect though and will require further
tweaking as it may result in the app becoming elevated higher
for much longer than necessary.

Change-Id: I62401cfabddf51b6f80b9bba8a358285b8cf9a51
Fixes: 72741441
Fixes: 72067231
Fixes: 72537465
Fixes: 72536347
Test: atest CtsUsageStatsTestCases:UsageStatsTests