Add subsections to the preference menu

Right now, there's 8 items in the profile preference menu. There can be more because of extensions. This is already a lot regarding https://lawsofux.com/millers-law/ that would advise to absolutely not go above 9 items.
The addition of preferences often ends up being a hassle because their organisation in UI do not allow a good user experience given the number of preferences we have (see https://forum.xwiki.org/t/shortcut-settings-position/14116 and https://forum.xwiki.org/t/changing-order-of-notification-autowatch/14342).
In order to improve the current UX of editing preferences, and make easier to add preferences in the future, a subsection level should be considered. This can be implemented using an accordion similar to the administration menu accordion.