This makes `browser_search_firefoxSuggest.js` more realistic by installing a
Nimbus experiment to change the Suggest scenario instead of manually setting the
scenario via the helper function. (The "scenario" just means whether Suggest is
enabled or not, basically. "history" means it's not enabled; "offline" and
"online" mean it's enabled. The difference between the latter two is that in
"online" the user has opted in to the Merino server, and that only means one of
the Suggest prefs is true instead of false.)
I noticed `browser_privacy_firefoxSuggest.js` does not check the visibility of
its Suggest section at all, so I added similar tasks to it and factored out the
common helpers into `head.js`.
Depends on D221097
Differential Revision: https://phabricator.services.mozilla.com/D221099
333d2a9ac1
