Notification history improvements

- don't keep readding history list onresume
- remove unstyled background (just use elevation for contrast for now)
- remove summaries from snoozed and recently dimissed because the user
wouldn't have seen their content

Test: manual
Fixes: 149499024
Change-Id: Ie43c752f42a7dfcac5ca9e3d118df07124daf974