replace old search engine dialog with listboxes with revealer
Note: This is not ready for review, I just targetted my work branch because Gitlab requires it. Now ready.
I submit this MR following the discussions that occurred in !722 (merged) (reveal each thread in chronological order to understand what ideas we've come up to).
pinging persons that have taken part in discussion !722 (merged) @exalm @mcatanzaro @jbrummer.