[web] Restyle Focus / Background buttons

Summary:
issue: https://linear.app/comm/issue/ENG-2791/restyle-focus-background-buttons
The icons were supposed to be dropped, and "Focus" was supposed to change to "Focused". Additionally some styles were changed.

Test Plan: Run web app, checked that buttons display correctly and work as expected.

Reviewers: michal, kuba, kamil

Reviewed By: kamil

Subscribers: ashoat, tomek, atul

Differential Revision: https://phab.comm.dev/D6734