This PR adjusts the "View More" button in the sidebar to expose threads
in batches of 5. Once you've expanded the whole available set, a button
to collapse the list back to the default number appears at the bottom.
Similarly, as soon as you expand the list even once, a button in the
group header shows up that does the same thing.
No release notes because this is still under feature flag.
Release Notes:
- N/A
Danilo Leal
fc39043b6c