Notification settings, importance and pre-O apps

- Show pre-O settings for the misc channel, should the app still have it
(versus the full channel settings)
- Fix the importance summmary text in various places
- Update the color of the blocked description text
- Fix what fields appear/disappear based on blocked status and importance

Fixes: 38177887
Bug: 38120923
Fixes: 38012300
Fixes: 37923612
Test: manual, with an O app, a pre O app that has channels, and a pre-O
app with no channels
Change-Id: I42965b81b795e8fb427f857c7766fe5480a99f2e