Fine tune what sensor use UI to show

Sometimes we want to show a dialog, sometimes a notification, sometimes
nothing.

- Also some minor UI tuning to match mocks.
- Also suppress dialog while dialog is visible and shortly after. This
  avoids a dialog directly after closing previous dialog.

Test: Triggered dialog. Needs exhaustive test of all
      cases though.
Bug: 162549680
Change-Id: I52ccd22858969823d8670a9e345d3da994ec1c19