Paginated app switcher

Still heavily WIP. Depends on at least !264 (merged) for continuous panel->favorites->app drawer opening, and !187 (closed) for app drawer pagination (since there's no app drawer atm to begin with), maybe more.

Currently implements pagination for running apps and in lockscreen !308 (merged). Also animates lockscreen opening and closing (todo: handle secondary screens too).

Also it currently removes click to close in overview, since it conflicts with swiping in PhoshPaginator. If it's wanted, it needs to be implemented in the paginator itself (and be done on release rather than press).

See also: https://source.puri.sm/Librem5/libhandy/merge_requests/297

CC @tobias.bernard