We reuse the existing logic for displaying and updating stream color
from the stream left sidebar.
Tests fixtures were extracted and updated for this commit.
* Add action to mute topics.
* We don't need to store muted data per topic as previously planned.
* Moved launch topic test to the top so that they run on non-modified
data.
* Show an empty overlay of recent topics.
* Register click event to open recent topics.
* Launch recent topics on "t" keypress.
This is based on the draft overlay.