style: Fix filters button style

See individual commits - since the app wasn't using AdwApplication I ported to it as a prerequisite.

Equivalent change in Calendar: gnome-calendar!297 (merged)

The libadwaita change in question is libadwaita!765 (merged)

I don't like to make behavior changes, but this one doesn't seem avoidable, and it only affects 2 apps - Calendar and Logs.