[Notif] Blocking helper basic metrics

Adding first pass of counters for basic actions taken with the blocking
helper. This includes:
- All notification dismissal events
- Shown event
- Dismissal via outside interaction
- Any button taps to dismiss
- Undo taps

Test: Via manual testing & updated tests (+added two new)
Bug: 74609669
Change-Id: I0adcfe03cfd10809ef7a2f13afbefcb420246a43