Inform UsageStatsManager about notification related events.

This change updates NotificationManagerService to inform
UsageStatsManager about notification posted/updated/cancelled
events.

Bug: 206518114
Test: atest services/tests/uiservicestests/src/com/android/server/notification/NotificationManagerServiceTest.java
Test: atest core/tests/coretests/src/android/service/notification/StatusBarNotificationTest.java
Test: atest services/tests/uiservicestests/src/com/android/server/notification/NotificationRecordTest.java
Test: atest cts/tests/app/src/android/app/cts/StatusBarNotificationTest.java
Change-Id: Idde09e4c72eb6a0635e4ee1c2c7e5887be170297