Log heads-up notification peeks using UiEvent logging.

This change adds a new UiEvent enum for NOTIFICATION_PEEK and logs it in the same places where we already count note_peek using MetricsLogger.

Test: atest HeadsUpManagerTest; manual verification via statsd_testdrive
Bug: 159697717
Change-Id: I10aebd73b4889f3f677de421018f39ce2ab8fb66
2 files changed