1854419 - Site identity https and other lazy pref getters should be in a module and not in self-deleting getters

Status: NEW

(Firefox :: Site Identity, task, P3)

Description

[:Gijs (he/him)]

Spotted as part of https://phabricator.services.mozilla.com/D179795 - we now have quite a few of these getters. This is a bit suboptimal because:

1. defining a lazy pref getter isn't particularly expensive so I'm not sure we couldn't just do this without the self-deleting getter
2. it's pretty verbose
3. we'll end up with 1 pref observer per window

ISTM that dumping all of these pref getters on some kind of utility module (maybe BrowserUIUtils, maybe UrlbarPrefs, maybe something dedicated?) would make this more manageable and solve all these issues. If we then lazy-load the module, the module itself can just define all the lazy pref getters in one go, and we'll only pay the cost the first time something has to check if https-first/only/whatever is turned on.