Improve how muted streams are displayed on Streams screen

In the subscribed streams UI, we should make the following changes to how muted streams are displayed:

1. Show the stream's privacy icon, not a special "muted" icon. This will make it possible for the user to tell what the stream's privacy is, and we already convey the fact that the stream is muted with fading.
2. Sort muted streams at the bottom of their section.

These changes will also make the mobile app UI more consistent with the left sidebar in the webapp.

CZO discussion